Wind Loads _ Anchor Bolt Design for Petrochemical Facilities

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Wind Loads andAnchor Bolt Designfor PetrochemicalFacilitiesPrepared by theTASK COMMITTEE ON WIND INDUCED FORCESand theTASK COMMITTEE ON ANCHOR BOLT DESIGN of thePETROCHEMICAL COMMITTEE of theENERGY DIVISION of theAMERICAN SOCIETY OF CIVIL ENGINEERS

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Published by

ASCE ::=-EngI~1801 Alexander Bell Drive

Reston, Virginia 20191-4400

Abstract:Current codes and standards do not address many of the structures found in the petrochemical indust!)".Therefore, many engineers and companies involved in the industry have independently developedprocedures and techniques for handling different engineering issues. This lack of standardization in theindustry has led to inconsistent structural reliability. These reports, Wind Loads on PetrochemicalFacilities and Design ofAnchor Bolts in Petrochemical Facilities, are intended as state-of-the-practiceset of guidelines in the determination of wind induced forces and the design of anchor bolts forpetrochemical facilities, respectively. These reports are aimed at structural design engineers familiarwith design of industrial-type structures.

Library of Congress Cataloging-in-Publication Data

Wind loads and anchor bolt design for petrochemical facilities / prepared by the Task Committee onWind Induced Forces and the Task Committee on Anchor Bolt Design of the Petrochemical Committeeof the Energy Division of the American Society of Civil Engineers.p. cm.ISBN 0-7844-0262-0I. Petroleum refineries--Design and construction. 2. Wind-pressure. I. American Society ofCivilEngineers. Task Committee on Wind Induced Forces. II. American Society of Civil Engineers. TaskCommittee on Anchor Bolt DesignTH4571.W55 1997 97-20890693.8'5--dc2l CIP

The material presented in this publication has been prepared in accordance with generallyrecognized engineering principles and practices, and is for general information only. This informationshould not be used without first securing competent advice with respect to its suitability for any generalor specific application.

The contents of this publication are not intended to be and should not be construed to be astandard of the American Society of Civil Engineers (ASCE) and are not intended for use as a referencein purchase specifications, contracts, regulations, statutes, or any other legal document.

No reference made in this publication to any specific method, product, process or serviceconstitutes or implies an endorsement, recommendation, or warranty thereof by ASCE.

ASCE makes no representation or warranty ofany kind, whether express or implied, concerningthe accuracy, completeness, suitability, or utility of any information, apparatus, product, or processdiscussed in this publication, and assumes no liability therefore.

Anyone utilizing this information assumes all liability arising from such use, including but notlimited to infringement of any patent or patents.

Photocopies. Authorization to photocopy material for internal or personal use under circumstances notfalling within the fair use provisions of the Copyright Act is granted by ASCE to libraries and other usersregistered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided thatthe base fee of $4.00 per article plus $.25 per page is paid directly to CCC, 222 Rosewood Drive,Danvers, MA 0 1923. The identification for ASCE Books is 0-7844-0262-0/97/$4.00 + $.25 per page.Requests for special permission or bulk copying should be addressed to Permissions & Copyright Dept.,ASCE.

Copyright © 1997 by the American Society ofCivil Engineers,All Rights Reserved.Library of Congress Catalog Card No: 97-20890ISBN 0-7844-0262-0Manufactured in the United States of America.

mical industry.levelopedrrdization in theochemicalJf-the-practice)lts foreers familiar

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Wind Loads on Petrochemical

Facilities

Prepared by the

Task Committee on Wind Induced Forces

The ASCE Petrochemical Energy Committee

This publication is one of five state-of-the-practice engineering reports produced,to date, by the ASCE Petrochemical Energy Committee. These engineering reportsare intended to be a summary of the current knowledge and design practice, andpresent guidelines for the design of petrochemical facilities. They represent aconsensus opinion of task committee members active in their development. Thesefive ASCE engineering reports are:

1) Design ofAnchor Bolts in Petrochemical Facilities

2) Design ofBlast Resistant Buildings in Petrochemical Facilities

3) Design ofSecondary Containment in Petrochemical Facilities

4) Guidelines for Seismic Evaluation and Design ofPetrochemical Facilities

5) Wind Loads on Petrochemical Facilities

The ASCE Petrochemical Energy Committee was organized by A. K. Gupta in1991 and initially chaired by Curley Turner. Under their leadership, the taskcommittees were formed. More recently, the Committee has been chaired by J. A.Bohinsky followed by Frank Hsiu.

Frank HsiuChevron Research and Technology Company

chairman

1. Marcell HuntHudson Engineering Corporation

secretary

Joseph A. BohinskyWilliam BoundsClay FlintJohn GeigelAjaya K. GuptaMagdy H. HannaSteven R. HemlerGayle S. JohnsonJames A. MapleDouglas 1. NymanNorman C. RennallsCurley Turner

Brown & Root, Inc.Fluor Daniel, Inc.Bechtel, Inc.Exxon Chemical CompanyNorth Carolina State UniversityJacobs Engineering GroupEastman Chemical CO.EQE International, Inc.J. A. Maple & AssociatesD. J. Nyman & AssociatesBASF CorporationFluor Daniel, Inc.

111

The ASCE Task Committee on Wind Induced Forces

This report is intended to be a state-of-the-practice set of guidelines It is basedon reviews of current practice, internal company standards, published documents, andthe work of related organizations. The report includes a list of references thatprovide additional information.

This report was prepared to provide guidance in the determination of windinduced forces for petrochemical facilities. However, it should be of interest tostructural design engineers familiar with design of industrial type structures and theapplication ofASCE 7 "Minimum Design Loads for Buildings and other Structures"to these type structures.

The committee would like to thank Ahmad Nadeem who was assisted greatly withour research on open frame structures.

Ch.

Chi

Norman C. RennallsBASF

chairman

Nguyen AiJohn GeigelUdaykurnar Hate~anuelHeredia

~arc Levitan~arvin LisnitzerJames~aple

Pravin PatelTed PuteepotjananAshvin ShahJerry SudermanJohn Tushek

Jon FergusonBrown & Root, Inc.

secretary

Jacobs Engineering GroupExxon Chemical Company~. W. Kellogg CompanyJohn Brown EngineersLouisiana State UniversityStone & Webster1. A. ~aple & AssociatesE.!. Du Pont De Nemours and CompanyRaytheon Engineers and ConstructorsFluor Daniel, Inc.Bechtel, Inc.Dow Chemical

Cha

Cha

Reviewers

AI WusslerDavid KemionJon Peterka

EI Paso Natural Gas / Gas Processors AssociationRP~ Engineering Inc.Cermak Peterka Petersen, Inc.

IV

J

J

J

Cha

1.1 Background I-I1.2 State of the Practice............................. 1-21.3 Purpose of Report 1-2

;. It is basedcuments, andferences that

CO:"TENTS

Chapter 1: Introduction . ......................... I-I

Chapter 2: Survey of Current Design Practices 2-1

tion of wind)f interest totures and ther Structures"

greatly with

2.12.22.32.4

Introduction 2-1Pipe Racks 2-1Open Frame Structures 2-4Pressure Vessels 2-6

Chapter 3: Comparisons of Design Practices 3-1

3.1 Introduction 3-13.2 Pipe Racks 3-23.3 Open Frame Structures 3-53.4 Pressure Vesse1s .3-11

Chapter 4: Recommended Guidelines 4-1

4.0 General 4-14.1 Pipe Racks '. 4-24.2 Open Frame Structures 4-34.3 Pressure Vessels .4-16Appendix 4A Alternate Method for Determining

Cf and Load Combinations for Open Frame Structures .4-21

Chapter 5: Examples. . 5-1

Appendix 5A Example - Pipe Racks 5-3Appendix 5B Example - Open Frame Structures..................... .. 5-9Appendix 5C Example - Pressure Vessels 5-19

Chapter 6: Research Needs . . ~I

6.0 General............................... . 6-16.1 Research Priorities 6-2

v

CONTENTS (Cont'd)

Nomenclature A-lGlossary...................................... . c B-1References C-1

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CHAPTER 1INTRODUCTION

This report is structured around generic types of facilities usually found in the processindustries:

a) Pipe support structures (pipe racks).b) Open and partially clad frame structures.c) Vessels (vertical, horizontal and spherical).

1.1 BACKGROUND

The basis and procedures for determining wind induced forces for enclosed structuresand other conventional structures are well documented in the engineering literature.These design basis and procedures have been adopted by ASCE and codified in ASCE 7and its predecessor documents. Other organizations have incorporated the majorprovisions ofASCE 7 into building codes, including the Uniform Building Code, StandardBuilding Code and BOCAINational Building Code. These building codes have beenadopted in ordinances and laws written by various local and regional jurisdictions.

The "Scope" statement for ASCE 7 indicates that the standard provides minimum loadrequirements for the design of buildings and other structures that are subject to buildingcodes. ASCE 7 does not adequately address open frame structures, structures withinterconnecting piping, partially clad' structures, and vessels with attached piping andplatforms. However, it does address enclosed structures, trussed towers and simplecylinders.

Wmd induced forces are typically calculated using the force equation from ASCE 7:

F=qzGCfA (II)

In this equation C\z is the velocity pressure component, G is for the gust component,Cf is the force'shape/drag/shielding component, and A is the area for which the force iscalculated. The velocity pressure component of this force (Clz) has three factors; theimportance of the structure, the surrounding terrain (exposure category), and design windspeed.

I-I

The selection of basic wind speed, importance factor, exposure category and gustresponse factor are defined in ASCE 7 and therefore are not discussed in detail. Forcecoefficients, tributary areas, and shielding are not clearly defined in ASCE 7 for industrial type structures and equipment. These load components are discussed in this report andrecommendations for selecting values are made. Since this report is intended tosupplement ASCE 7, the designer will be referred to that document when it provides theappropriate information. The nomenclature and glossary used in the recommendations ofthis document mirror those found in ASCE 7.

1.2 STATE OF THE PRACTICE

This study is based on current industry practices in the design of petrochemicalfacilities. The practices are generally based on a company's experience and the desire toprovide an economical facility that provides a margin of safety that is consistent with theperceived risk. These practices, as interpreted by the committee, are quite varied. For agiven type of structure, the practices currently in use can result in design wind inducedforces that vary by factors as large as 5, when using the same basic wind speed andexposure category.

1.3 PURPOSE OF REPORT

It is intent of this committee that the publication of this report will result in a moreuniform application of practices across the petrochemical energy industry. In order tofacilitate this goal a set ofrecommended guidelines is presented as part of this report.

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CHAPTER 2SURVEY OF CURRENT DESIGN PRACTICES

2.1 INTRODUCTION

Thirteen design practices, for wind on pipe racks, open structures and pressurevessels were reviewed. These design practices were obtained from various operatingcompanies and engineering contractors working in the petrochemical industry.

All but one of the design practices reviewed were based on the wind loadingprovisions of ASCE 7-88, "Minimum Design Loads for BUilding.~ and OtherStructures" or its predecessor (ANSI A58.J). The recommended wind speed, meanrecurrence interval and exposure coefficient (based on terrain exposure C, openterrain) were generally the same.

The building classification, used for the importance factor, by all of the designpractices was ordinary structures (Category I). However, a few practices chose touse the essential facilities category (Category III) for particular structures.

2.2 PIPE RACKS

Most of the design practices treated the rack structure as an open frame structurewith additional loads for pipe and cable trays. Since open frame structures arediscussed in another section of this report the wind loads applied directly on thestructure will not be discussed here. Table 2.1 presents the survey results in tabularform.

The major differences between design practices is covered in Table 2.1. Notethat the determination of force coefficient, effective area, and shielding is notaddressed in ASCE 7 for piping and cable trays in a pipe rack therefore the followingdefinitions are used Table 2.1 as defined by the respective design practice.

A Tributary area (sq. ft).d Depth ofcable tray (ft).

2-1

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TABLE 2.1Survey Of Piperac:k Design Prac:tic:es

DESIGN BASIS FORCE TRlBlITARY SHIELDING/COMMENTSGUIDE CODE COEFFICIENT AREA

Nl ASCE 7-88 Part I Part I Shieldin8 is taken care of in the Force

Cf= 0.7+W/25D < 2 for pipes A = D·L for pipes Coefficient.

Cf= 2.O+W/25d < 4 for cable tray A = d·L for cable tray

Part npartn Part 1II

Cf= 1.3A=H·L Use the smaller value from Purl I or II

N2 ASCE 7-88 Cf - 0.8 (Includes the Gust Factor) for A = D ·m·L for pipes Shielding is included in the factor IIIaV8pipes. A = d"m·L for cable tray

N3 ASC£ 7-88 Cf- 1.1 "tan 100- 0.19 for pipe and cable A=W·L Shielding is included in Cram} A. 'Ille

tray or force is based on the wind at 8 10° angle

or A= D"L of incidence anu a force coclliciclll of 1.1.

Cf= 0.8 Faree shall not be less than on the largest

pipe alone.

N4 ANSI A58.1 '82 Not specified. Not specified. Does noladdrcss pipe or cable tray.

NS ASCE 7-88 Not specified. Engineer shall interpret Area is based on an angle of Shielding is included in area.

ASCE. incidence of,"10· and a 5 dia.

shielding cone.

Alternatively A = (D+(W-D)sin IS.2·jeos 10· L Alternately

Cf=0.31 forW"4fi(1.22m) = D+O.25(W-D) L Shielding is included in force codlicicnt

= 0.22 for W" 16 fi (4.88 m) Alternatively and Mea.

A=W·L Does not address cubic tray

N6 ASCE 7-88 Cf= 0.7 for D;lq,;> 2.S A - [I+W/6DJ·D"L Wind is based on Wl angle of incidence of

= 1.2 for D;lq, $25 100, Does not address cable tray.

TABLE 2.1

~ 1.2 for D~q, ,;25 10°. Does not address cubic lray. I

TABLE 2.1

Survey Of Piperack Design Practices (cont'd)

NW

DESIGN BASIS FORCE TRIBUTARY SIIIELDING/COMMf;NTSGUIDE CODE COEFFICIENT AREA

N7 ASCI' 7-88 Cf- 0.7 for pipes A - D 'SM'L for pipe Shielding is incorporated in factor SM foravg

Cf~ 1.75 for cable trays A ~ d'(l+(N-I)n )'L for cable trays pipes and n for cubic trays.

N8 ASCI' 7-88 Not specified. Not specified. Uses Exposure C outside batterylimits and B inside.

~9 ASCI' 7-88 From rable 14 ofASCI' 7-88 A - (Dt 10% of usable width Shielding is included in urea.

For pipes use Cf= D,JQ,"> 2.5 for pipe or cable tray)·L.

For cable tray use Cf for flat surfaces Uses Exposure C or B.

NIO ANSI A58.1 Cf - 1.0 when used for an components or A - 3'L for racks> 12 II (3.66 m) Shielding is induded in oren.

1982 use Cf values from ANSI when applied to A ~ 2'L for racks < 12 II (3.66 m) Does not address cable tray.

individual components.D > 16 inehes need special

consideration.

Nil ASCI' 7-88 Cf~ 0.7 A - 3'L for racks W< 12 II (3.66 m) Shielding is included in area

A ~ 2'L for racks 12<W<20 II (166- Does not address cable lray.

6.10 m)

#12 ASCI' 7-88 Not specified. Not specified.

N13 UBC or Cf-2 A-D'L Shielding is included in force coeniciclil.

ANSI A581 Does not address cable Iray.

1982-

D,vg Average diameter of all pipes greater than 6 in. (0.15 m) plus the averagediameter of the four largest pipes (ft).

D Diameter of the largest pipe (ft).H Distance from the bottom level to the top level of the pipe rack (ft).L Pipe rack bent spacing (ft).m A factor to account for shielding, varying from 1.0 for one pipe to 3.3 for

12 pipes or more.n A shielding factor for cable trays varying depending on the ratio oftray

height to spacing between the adjacent trays. Ranging from 0 to 0.5.N Number ofcable trays.qz Velocity Pressure (pst)SM A factor to account for shielding, varying from 1.0 for one pipe to 4.5 for

12 pipes or more.W Width of pipe rack (ft).

2.3 OPEN FRAME STRUCTURES

The design practices divide their evaluation of open frame structures into threegeneral areas:

• Equipment• Structural framing• Piping & misc. attachments (ladders, handrail etc.)

Generally, the wind load on the structure and equipment supported by thestructure are considered separately. No shielding effect between equipment orbetween structure and equipment is considered. However, several practices place anupper bound on the total wind load on the structure and therefore indirectly reflectshielding.

Wind loads on equipment are computed either from principles of ASCE 7 or asdescribed in the following section on pressure vessels. Additionally, other than whatwas discussed in the previous section on pipe racks the differences between how thedifferent practices handled piping and miscellaneous attachments in open framestructures was minor. Therefore, this section concentrates on the differences on howthe structural framing is evaluated in the various design practices. Table 2.2 presentsthe survey results.

In the case of flexible structures, the procedure given in the commentary sectionC6.6 ofASCE 7-88 is generally, with one exception, recommended by each standard.

24

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TABLE 2.2Survey of Design Practices for Open Frame Structures

:1 Design Basis CommentspracticeI Whilbread & AXE 7 Whitbread is the basis for shielding factors, For six frames or

less an enclosed. structure is upper boWld. There is provision for, increasing the force coefficient for more than 6 frames.

Considers load out of horizontal plane,

The area considered is the protected area of the windward frame.2 ASCE 7 & NatIOnal Force coet1icient is based on National BUilding Code oJCanada

BUilding Code ojCanada

3 ASCE 7 & Georgiol Force coet1icient is based on Georgio/Vickery/Church,Vickery/Church

A single Cf factor is considered in the calculation of wind on thestructure

Cf ~ 1.8 for all the framing members and 1.6 for ladders andolatforms,

4 ASCE7 Provides simplified combined load coefficient for the gross areaof the structure

5/6 Whilbread & ASCE 7 Whilbread IS the baSIS for shielding tactofS. Ine total wind forceis limited to the upper bound of wind load on an enclosedstructure that would completely envelop the structure andattachments.

7 ASCE7 The calculation of wind load considers the projected area of:

a) the deepest girder for a Hoor levelb) depth of flooringc) piping and electrical as a percentage of the gross aread) handrails perpendicular and parallel to the direction of wind,e) stairsf) projected area of all colwnns and all vertical bracing (no

shieldinR)8 ASCE7 Use Exposure B for pipe racks. No other guidelines provided.9 ASCE 7 & ASI 170, Cfis taken from Table 14 and 15 ofASCE 7-88.

Part 2, StandardsAssociation of Shielding is based on ASff70, Part 2, Standards Association ofAustralia Australia

10/11 ASCE7 Proprietary, SImplified "cflective" force coefficient applied to thewoss area of the structure.

12 ASCi<' 7 CfisbasedonTable 14ofASCE7-88

ProprietalV force cocrticicnt armlicd to the windward frame.13 ANSI 0458. 1 The force coefficients used for apen frame structures and pipe

racks arc 1.3 for the windward frame, 0.8 for the 2nd frame, and

05 for the 3rd and suceeedin~ frames.

2-5

2.4 PRESSURE VESSELS

The \Vind load determinations for vertical and horizontal pressure vessels for alldesign standards are predominantly in accord with ASCE 7-88, however there aresome key differences in the approaches taken.

The main differences involve the effects of platforms, piping, ladders, nozzles andinsulation. These differences have the most effect on total shear and moment forhorizontal vessels. For platforms, some of the guidelines use plan projections ofplatforms, some use percentage of vessel diameter, some use vertical projected area,and some use projection of individual members. Most of the guidelines add apercentage ofvessel diameter or I to 2 ft (0.30 to 0.61 m) to the diameter to accountfor appurtenances such as insulation, nozzles, and ladders. For some guidelines largepipe is accounted for separately and for others a percentage of the vessel diameter isused. Force coefficients for pipe vary from about 0.6 to 1.6 (most being about 0.7).The coefficients for the vessel itself are generally in line with ASCE 7-88, Table 12,but values for various surface roughness differ.

Most design practices state that if a vessel has an unusual amount of piping,platforms, etc. or is of an unusual configuration, the components should be figuredseparately instead oflumping them with a simplifYing factor.

Most design practices require calculation of a gust response factor for flexiblestructures if the hID ratio exceeds 5 or the fundamental frequency is less that 1 Hz.Table 2.3 presents the survey results in tabular form.

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TABLE 2.3

Survey of Design Practices For Vessels

Design NotesPractice

I. VerticJll Vessels - Afbased on increased shell diameter to account for rnanw.>ys,ladders, platforms and small piping. Cr is for moderately smooth cylinders, but hIDbreak points are at 4 and 16 in lieu of? and 25 (as in ASCE 7 -88 Table 12).

Horizontal V""",,1s - Afbased on increased shell diameter to account for supports,piping and other attachments. Cr is 0.5 or 0.6 depending on slenderness ratio fortransverse wind; and, for longitudinal "'ind. 1.0 for flat heads and 0.5 for roundedbeads.

2. VerticalV~ - Afis based on aetuaI shell diameter. Cr is the larger of that forrough surfuces or that for moderately smooth surfuces multiplied by a factor based onvessel diameter, to cover ladders and piping. Platforms are figured separately and Af isbased on 1/2 the platform plan area.

HorizontalV~ - Platforms figured separately and Afis based on 1/2 the platformplan area.

J. Vertical V""",,1s - Ar for h<75 ft.(22.86 m) based on vessel diameter multiplied by afactor depending upon vessel diameter to cover appurtenances. Cf is for roughswfaces. Arfor h>75 ft. (22.86 m) is based on aetuaI vessel diameter. Cf is for roughsurfuces. Platforms, ladders and piping figured separately.

Horizontal V""",,1s - Af is based on increased vessel diameter to cover rnanw.>ys,platforms and piping.

4. No simplifying assumptions presented for vessels.

5. VerticalV~ - Af is actual vessel diameter. Cf for very rough cylindelS is appliedover a portion (not less than 50"10) of the vessel diameter to account for ladders,platforms and piping with diametelS less than 5% of the vessel diameter. Cf formoderately smooth cylinders is applied to the remaining shell diameter. Area of pipingwith diametelS greater than 5% ofthe vessel diameter is added and Cr is 1.4.

Horizontal Vessels - No simpluying assumptions presented.

6. Vertical Vessels - Ar is actual vessel diameter. Cr for very rough cylinders is appliedover a portion (not less than 50%) of the vessel diameter to account for IaddclS.platforms and piping with diameters less than 5% of the vessel diameter. Cf formoderately smooth cylinders is applied to the remaining shell diameter. Area forpiping with diameters greater than 5% of the vessel diameter is added and Cfis 1.4.

Horizontal Vessels - No simpliJYing assumptions presented.

2-7

TABLE 2.3 (Cont'd)

Survey of Design Practices For Vessels

Design NotesPractice

7. No simpJ.i1Ying assumptions presented for vessels.

8. No simpJ.i1Ying assumptions presented for vessels.

9. Vertical Vessels - Afbased on vessel diameter multiplied by a factor depending uponvessel diameter to account for nozzles, manways, piping and insulation. Cr is formoderately smooth cylinders.

Horizontal Vessels - Same approach as for vertical vessels is used.

10. Vertical Vessels - Afis based on vessel diameter plus largest pipe plus 1.0 ft. (0.3 m)to cover ladders and small piping. Cr is for moderately smooth cylinders. Platforms arefigured separntely and Af is based on 1/2 the platform plan area.


11. Vertical Vessels - Aris based on vessel diameter plus largest pipe plus 1.0 ft. (0.3 m)to cover ladders and small piping. Cr is for moderately smooth cylinders. Platforms arefigured separntely and Ar is based on 1/2 the platform plan area.


12. Vertical Vessels - Afis based on vessel diameter multiplied by 1.2 to account forpiping and other appurtenances.

Horizontal Vessels - Afis same as for vertical vessels. Cris 0.8.

13. Vertical Vessels - Ar is based on the vessel diamcter plus the largest pipe plus afactored platform width.

Horizontal Vessel. - Afis thc vessel diamcter multiplied by a factor dependent onvessel diameter.

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CHAPTER 3COMPARISONS OF DESIGN PRACTICES

3.1 INTRODUCTION

Since shielding is sometimes included in the force coefficient and other times in theprojected area, the design practices cannot be compared by simply looking at the variouscomponents ofwind load (i.e. force coefficient, projected area, and shielding). Therefore,typical examples of structures encountered in practice have been selected. Theseexamples are used to create tables that compare the applied wind forces for each designpractice. The tables also include the wind forces resulting from the methods proposed inChapter 4 used with ASCE 7-88, to match the design practices, and the proposedmethods used with the current standard, ASCE 7-95.

The definitions and values for structure classification categories and correspondingimportance factors as well as the wind speed map have changed in the newer version ofthe standard.

• Using the definitions of ASCE 7-88 structures were assumed to be classified asCategory I ('ordinary') structures (ASCE 7-88, Table 1). In ASCE 7-95, there is thepossibility of choosing between Category II and Category III for the wind inducedforces. Category II is now 'ordinary' structures, what used to be called Category I inASCE 7-88. Category III includes "...structures that represent a substantial hazard tohuman life in the event offailure."

• In ASCE 7-95, the wind speed map has been changed from fastest mile to a threesecond design wind velocity. There were also corresponding changes made in thevelocity pressure exposure coefficients and gust factors.

The structures used in the comparisons were set in a fictitious plant in an arbitrarylocation. The location chosen was Lake Charles, Louisiana (in southwest Louisiana,about 20 miles from the gulf coast). The wind speed and importance factor used in the

3-1

Case I

Case IICase III

Case IVCase V

comparisons were 96 mph (43 rnIs) and 1.04 respectively (ASCE 7-88, Figure 1 and Table5). Terrain exposure C was assumed (flat, open terrain with scattered obstructions).

Wmd loads calculated using the proposed guidelines of Chapter 4 with ASCE 7-88and ASCE 7-95 with the 'ordinary' structure classification differed only slightly. Thedifferences are due to the change in the wind speed definition and the vertical velocityprofile between the standards. Wind loads using ASCE 7-95 and Category III structureswere 15% greater than those for an 'ordinary' structure classification, due to increasedimportance factor.

3.2 PIPE RACKS

The following pipe and cable tray configurations (pipe Load Cases) were used forcompanson.

20 ft (6.10 m) wide rack with one 48 in (1.22 m) pipe & fourteen 9 in(0.23 m) pipes20 ft (6.10 m) wide rack with fifteen 12 in (0.30 m) pipes5 ft 6 in (1.68 m) wide rack with one 24 in (0.61 m) pipe & two 12 in(0.30 m) pipes4 ft 6 in (1.37 m) wide rack with three 12 in (0.30 m) pipes20 ft (6.10 m) wide rack with one 36 in (091 m) pipe, two 24 in (061 m)pipes, four 12 in (0.30 m) pipes, & six 9 in (0.23 m) pipes

Cable Tray 20 ft (6.10 m) wide rack with two 36 in (0.91 m) trays, one 24 in (061 m)tray, two 18 in (0.46 m) trays, two 12 in (0.30 m) trays, & two 6 in (0.15m) trays, all 6 in (0.15 m) high

These pipe load cases are illustrated in Figure 3.1. Table 3.1 summarizes the wind forcescalculated using the design practices. In order to have a common basis for comparison,the following criteria were used:

• Height of the pipe or cable tray level used for calculations: 30 ft (9.14 m)• Velocity Pressure Exposure Coefficient (for z = 30 ft (9.14 m»: K, = 0.98• Velocity Pressure: qz = 0.00256 K,(IV)' = 25.1 psf(1.2 kN/m')• Gust Response Factor: G. = 1.26• Design Wind Pressure: qz C1}, = 31.6 psf(1.51 kN/m')

3-2

rld Tables).

':E 7-88ly Thevelocity

:rueturesrlcreased

used for

een 9 in

2'-3'),'~ <-

s!~: "; -2" '

i(): I ., . ,- ::' "i"5 "

, .

i OooQoQOOOOOOOO

D '-' 02C'-0'

1'- 3'- '---I I 17'-6'I . is . 12' DiA PIPES I

I I ! IIOOOOOOQ9ooooooolD DI I

20'-el'

I I

va 12 in

[0.61 m)

(0.61 m)in (0.15

~;:T10 001

~;~ CASEI ~J I ,.~-wT

CASE IV

Id forceslpariSOn,

Figure 3.1 Comparison - Pipe Load Cases

3-3

This section is limited to v,;ind force on the piping or cable trays only; therefore, windon the structure has not been included. In addition to the design practices, load cases Aand B are included to establish lower and upper bound values for wind forces onpipes. Basis A is wind on the largest pipe only and can be thought of as a minimumprobable load (lower bound). Basis B is full wind on all the pipes (no shielding) andcan be thought of as the maximum probable load (upper bound).

TABLE 3.1 Design Practice Comparisons - Pipe Rack Wind Forces

VALUES ARE IN POUNDS PER LINEAR FOOT OF PIPE OR CABLE TRAY(Note 1)

PIPE LOAD CASES CABLEBASIS TRAYS REMARKS

I II III IV V

A 66 22 44 22 50 - Lower bound

B 299 332 88 66 343 - Upper bound

#1 114 48 51 28 92 57

#2 64 66 59 44 104 (Note 3)

#3 121 121 51 27 121 121

#4 - - - - - - (Note 2)

#5 167 127 66 41 167 (Note 3)

#6 167 127 66 41 167 (Note 3)

#7 102 100 65 49 156 61

#8 - - - - - - (Note 2)

#9 202 97 70 34 169 121

#10 179 95 84 63 190 (Note 3)

#11 93 93 62 62 93 (Note 3)

#12 - - - - - - (Note 2)

#13 253 63 126 63 190 (Note 3)

3-4

TAl

B

Avg.1#1

ReconDlPr:

(Seec

Notes

1 To

2 Un

3 Thi

3.3 0

TheFigurelm) x 8:

Thl(3.05 n(610 nm) lon~

Me:

\',ind;es A~s onmum) and

S

TABLE 3.1 Design Practice Comparisons - Pipe Rack Wind Forces (Cont'd)

VALUES ARE IN POUNDS PER LINEAR FOOT OF PIPE OR CABLE TRAY(Note I)

PIPE LOAD CASES CABLEBASIS TRAYS REMARKS

I II III IV V

Avg. Practices 146 94 70 45 145 90#1-#13

133 66 56 32 III 158 ASCE 7-88

RecommendedDesign

129 64 55 31 107 153 ASCE 7-95Practice(See Chap 4) Category II

148 74 63 36 123 176 ASCE 7-95Category III

Notes to Table 3.1

1 To convert pounds per foot to newtons per meter multiply values by 14.6.

2 Unable to calculate load values from the provided documents.

3 This design practice does not address cable trays.


The plan and elevation views of the structure used for comparison are shown inFigures 3.2,3.3 and 3.4 The structure considered was 40 ft (12.19 m) x 40 ft (12.19m) x 82 ft (24.99 m) high, with three open frames in the direction of wind.

The structure supported two horizontal vessels (4 ft (I.22 m) diameter x lOft(305 m) long & 16 ft (4.88 m) diameter x 32 ft (9.75 m) long) on level 20 ft 0 in(6.10 m) and three horizontal exchangers (2 @ 10 ft (3.05 m) diameter x 24 ft (7.32m) long & 2 ft (0.61 m) diameter x 20 ft (6.10 m) long) on level 48 ft 0 in (14.63 m).

Member sizes were assumed as follows:

ColumnsBeams EI20 ft 0 in (6.10 m) -

12 in x 12 in (0.31 m x 0.31 m)W36

3-5

/'H-------H--------HII ----------, C

~

\'lIND

r-,! -.; \

U

I /'-----~"-- J+--(~,

H H,,,

0 .';\V

•

Elev 48' -W

WIND

--f+--Ni ~,,

(:),,

o

H --====-- H -------1+11 -- -----(0/

o~ w':'~u~

<t~N ;, ~

~;:W bwu

.u'" ;::

L~x _

"NUU N

I-1---- HH

I--' Jlc:J

'" '" Iii,i,

o

lFigure 3.2 Example for Open Frame Structure Comparison - Arrangement Plan

Fi

3-6

.'

82 0'~ Lev -N~c / , , /1:8

~'" I, '., I 4-~" ~,/,:2 i w12 -

i / ",I , xI

i " ~j ",""2 'tIl2

k,

i,

iI

I

:=:=:~-=~~:=:=:~:i:=:~:=:=:~'='=:~:=: I, ELev 48'-

"8 wle

/c

lWI2 / WI2

//,.,

/ .. ' WI2~!WI2 /

~

/

~.=:=:c:=:=:~:l:=:~-=:=:~:=:=:~:=: I20'-0·1I I I I I I I j I[!ev

W36/ ~w36

~.,..I$-~~

WI2

!)a ,WI2

""/

/

/ ,~/ [lev 0"-""

f-

20'-0' 20'-W

(0 (~

an

Figure 3.3 Example for Open Frame Structure Comparison - Column Line 3

3-7

1.

3.

2.

Foof the(see e,

Thelectricdesign20%0

Thresults

ELev 20'-0'.:cc..::..c...=--"- _

::lev ~8'-0'-------

ST AIR/~ TOWER

(

EleJ 82-2'

W10

W'0

r----T"--i-------_.-

/

W16

~,'O

WI~

~ ..?B_ ... _

~',Vl:~.

:=:~:=:=:~:=:=:~:I I I'

.'-.

WI6

£1

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V2

__ ..' - W10

--·-·r·-·-·r·----r_._._._._-_._-_._-I I I

'-'-'r-~'--r-----,-._---------~-_._._-

I

i11i

[lev 0' -0'

Figure 3.4 Example for Open Frame Structure Comparison - Column Line A

3-8

BeamsEI48ftOin(l463m)- WI8BeamsEI82 ft 0 in (2499 m)- WI8Braces \V8Intermediate Beams \V12

For this comparison the windward frame was column line 3. The projected areasof the stair tower members were included in the calculation of the windward frame(see example section 5B.I for details).

The calculations considered provisions for. the projected area for piping andelectrical trays per the design practices. If these provisions were not defined in thedesign practice the reviewers chose a projected area of piping and electrical to be20% of the equipment area.

The results of tota! wind force are tabulated in Table 3.2. The comparison of theresults of the calculations categorizes the design practices in three groups.

1. Some companies use Cf factor based on Table 15 of ASCE 7 and consideronly first two frames, resulting in lower wind force.

2. Some companies limit total wind force by an upper bound based on a totallyenclosed structure. The results of total wind force are almost the same.

3. Some companies consider multiframe open structures with or withoutshielding. No upper bound is considered. Generally the Cf factor consideredfor the open frame structure remained constant for these practices. However,the areas exposed to the wind differed and hence the results.

3-9

TABLE 3.2 Design Practice Comparisons - Open Frame Structure Wind Force

VALUES ARE BASE SHEAR IN KIPS(Note 1)

DESIGN COMBINATION COMBINATIONPRACTICE A B COMMENTS

(Note 2) (Note 3)

#1 NA 162 See Note 4.

#2 122 160 Open frame structureconsidered.



#5 130 141 See Note 4.

#6 130 141 Same as Design Practice #5.


#8 lOS 129 Two frames considered perTable IS of ANSI.

#9 97 120 See Note 4.

#10 93 116 Has used an effective forcecoefficient other than fromASCE or ANSI.

#11 NA 90 Effective force coefficientbased on the solidity ratio ofthe structure.

#12 157 182 Similar frames assumed in anopen frame structure.


Average 115 136

Recommended 123 147** ASCE 7-88See Chap 4

124 148** ASCE 7-95 Category 11

143 170** ASCE 7-95 Category III

3-10

3.4

3.4.

consho'wernun

tharRecthe ~

Iandfom0.91flexicalctfacte

1.

Notes to Table 3.2

1 To convert kips to kilonewtons multiply,a1ues by 4.448.2 Combination A includes only wind on the structural frame. When NA is

reported the design practice did not segregate the results betweenequipment and the structure in this case.

3 Combination B includes wind on the structural frame, equipment, piping, andelectrical.

4 Limited by the upper bound which is typically an enclosed structure.

** Must be applied simultaneously with partial wind load on the other structuralaxis. See section 4.2.6 and Appendix 4A


3.4.1 Vertical Vessels

In order to have a common basis for comparison, a set of criteria and vesselconfigurations were developed. The example vertical vessel along with its criteria isshown on Figure 3.5. Calculations of wind forces from contributing componentswere prepared and combined into loads at the base of the vessel. Table 3.3 presents anumerical comparisons.

Forces for rigid and flexible structures (fundamental natural frequency greaterthan or less than I Hz, respectively) were calculated for each design practice.Recommendations for dynamic analysis due to vortex shedding, flutter, etc. is beyondthe scope ofthis report.

For the selected tower the empty natural frequency was 1.18 Hz, more than 1.0,and per ASCE 7 a gust factor for rigid structures is therefore used to obtain windforces. When the operating weight of the tower was used, the natural frequency was0.91 Hz. Since thi~was less than 1.0, it was necessary to calculate a gust factor forflexible structures (G). Methods in the design practices were used, when available, tocalculate G. If the design practice did not provide a method to calculate the gustfactor, the method in ASCE 7 commentary was used.

3-11

(!'lJ lNSUlAHONJSHELL THICKNESS'!'EMPTY 'WEIGHT: 1.5 X '11I'1. DF ShELLOPERATlNC ~EIGHT ' [MPTY • 30% FULL WATER

t:: :i El.IOO· 60° PlATFffiH

c: :J fj 75" 60° PI AlfDRM

18' PIPE

~I- c \._.....I"':o!J=!E~LLIJ:'YW\l!180a PLATfORM

'~~ OM " '0'

~I

Figure 3.5 Example for Vertical Vessel Comparison

3-12

,,,.."CI

~..•~•.~t~

1_-Table 3.3 Design Practice Comparison - Vertical Vessel Wind Load

___J

VJ,'-'

VALUES ARE BASE SHEAR IN KIPS(Note I)

DESIGN BASED ON A RIGID VESSEL BASED ON A FLEXIBLE VESSELPRACTICE

NO.TOTAL PLATFORM VESSEL+ PIPE TOTAL. PLATFORM VESSEL+ PIPESHEAR SHEAR MISe. SHEAR SHEAR SHEAR MISC. SHEAR

SHEAR SHEAR

#1 49.3 3.3 45.3 0.8 62.4 4.2 57.2 \.0(Note 3) (Note 5) (Note 3) (Note 5)

#2 50.4 5.3 45.2 (Note 4) 63.9 6.7 57.2 (Note 4)

#3 65.3 4.6 53.9 6.9 79.7 5.6 65.7 8.4

#4 (Note 2)

#5 6\.9 12.5 36.3 13.2 77.1 15.6 45.2 16.4

#6 6\.9 12.5 36.3 13.2 77.1 15.6 45.2 16.4

#7 (Note 2)

#8 (Note 2)

#9 55.0 9.9 40.0 5.1 68.8 12.4 50.0 6.4

#10 50.1 5.4 39.3 5.4 59.8 6.6 46.8 6.4

#11 50.1 5.4 39.3 5.4 59.8 6.6 46.8 6.4

#12 53.5 12.4 34.3 6.9 66.4 15.3 42.5 8.5

#13 48.7 3.9 38.6 6.3 55.5 4.4 44.0 7.2

w,-.f:o

Table 3.3 Design Practice Comparison - Vertical Vessel Wind Load (Cont'd)

VALVES ARE BASE SHEAR IN KIPS(Note I)

AVERAGE & BASED ON A RIGID VESSEL BASED ON A FLEXIBLE VESSELRECOMMENDED

PRACTICE

(SEE CHAPTER 4) TOTAL PLATFORM VESSEL+ PIPE TOTAL. PLATFORM VESSEL+ PIPESHEAR SHEAR MISC. SHEAR SHEAR SHEAR MISC. SHEAR

SHEAR SHEAR

Average#I-#13 54.6 67.1

Based on ASCE 7-88 55.6 (Note 4) (Note 4) (Note 4) 69.3 (Note 4) (Note 4) (Note 4)Simplified

Based on ASCE 7-88 51.9 6.4 39.4 6. I 64.7 8.0 49.1 7.6Detailed

Based on ASCE 7-95 56.1 (Note 4) (Note 4) (Note 4) 68.0 (Note 4) (Note 4) (Note 4)SimplifiedCategory II

Based on ASCE 7-95 52.4 6.5 39.9 6.0 63.6 7.9 48.3 7.3Detailed

Category II

Based on ASCE 7-95 64.5 (Note 4) (Note 4) (Note 4) 78.2 (Note 4) (Note 4) (Note 4)Simplified

Category III

Based on ASCE 7-95 60.3 7.5 45.9 6.9 73. I 9.1 55.6 8.4Detailed

Category III

en ."" ~ -

Notes to Table 3.31 To convert kips to kilonewtons multiply values by 4448.2 No guidance provided for vertical vessels.3 Load from platform at elevation 150 ft (45.72 m) only - Other platforms

are included in shell loads.4 Included in shell loads5 Considers only forces generated above elevation 150 ft (45.72 m)

Remaining forces are included in shell loads

The criteria used for comparison of wind forces on vertical vessels are as follows:

• Circular platforms are 3 ft (0.91 m) wide measured from the edge of thetower.

• Vertical part of 18 in (0.46) diameter pipe acts as part of tower.• Add 50% of shell weight to cover internals and miscellaneous.• Assume vessel is 30% full of liquid (Specific Gravity = 1.0) during

operation.

Table 3.3 presents the numerical comparison for each design practice. Baseshears from wind forces varied from 48.7 to 65.3 kips (217 to 290 kN) for an emptyvessel and 55.5 to 79.7 kips. (247 to 355 kN) for an operating vessel.

3.4.2 Horizontal Vessels

The same approach as vertical vessels was used to evaluate the loads onhorizontal vessels. However, many of the design practices do not have explicitguidelines for horizontal vessels.

The horizontal vessel configuration used for the calculations is shown on Figure3.6.

Table 3.4 presents the numerical comparison for each design practice. Baseshears for transverse wind loading varied from 10.9 to 19.0 kips (48.5 to 84.5 kN).

3-15

i5' - 0"-1--__01- 5'-W22'-0"22'-0'

/

!=

"

25--W 25--Wt------'"'-"------r-----"-''--''----r-r- J - 1YP,

15'-0' : 15'-0' I -II

l(AGED I I I; LADDER

PLATFORM-~C:=:=:=:==:=I: :==:===:=. I

i\ VN,_________________ - { L }-_

!/'--- 2:1 HEADS I'.. : /'HP, I rn

~"TYP"

--u-- l' TYP.-=--!f--r-'-J----=_N~~ ,

,,

0;--+- --(12- D.o_ lANK---

':' N \

-~

Figure 3.6 Example for Horizontal Vessel Comparison

3-16

w,--.J

Table 3.4 - Design Practice Comparison - Horizontal Vessel Wind Load


DESIGN TRANSVERSE DIRECTION LONGITUDINAL DIRECTIONPRACTICE

NO.Total Platform Ladder Suppon Vessel Total Platform Ladder Suppon VesselShear Shear Shear Shear Shear Shear Shear Shear Shear Shear

#1 10.9 (Note 3) (Note 3) (Note 3) 10.9 2.2 (Note 3) (Note 3) (Nole 3) 2.2

#2 19.0 4.3 (Note 3) (Note 3) 14.7 6.6 4.3 (Note 3) (Note 3) 2.3

#3 16.2 (Note 3) (Note 3) (Note 3) 16.2 4.4 (Note 3) (Note 3) 1.6 2.8

#4 (Note 2)

#5 (Note 2)

#6 (Note 2)

#7 (Note 2)

#8 (Note 2)

#9 19.0 5.9 1.3 0.2 11.6 (Note 4)

#10 14.6 4.0 0.6 0.2 9.8 (Note 4)

#11 14.6 4.0 0.6 0.2 9.8 (Note 4)

#12 16.6 3.2 (Note 3) 0.8 12.6 (Note 4)

#13 18.2 2.2 (Note 3) (Note 3) 16.0 (Note 4)

w,-0<>

TABLE 3.4 - Design Practice Horizontal Vessel Wind Load Comparison (Cont'd)


AVERAGE & TRANSVERSE DIRECTION LONGITUDINAL DIRECTIONRECOMMENDED

DESIGN PRACTICE

(SEE CHAPTER 4) Total Platform Ladder Support Vessel Total Platform Ladder Support VesselShear Shear Shear Shear Shear Shear Shear Shear Shear Shear

Average # I - #13 16.1 4.4

Based on 14.7 3.8 (Note 3) 0.3 10.6 8.3 1.3 (Note 3) 5.1 1.9ASCE 7-88

Based on 15.83 4.09 (Note 3) 0.43 11.30 10.0 1.39 (Nole 3) 6.61 2.0ASCE 7-95

Cate~ory "

Based on 18.2 4.7 (Note 3) 0.5 13.0 11.5 1.6 (Note 3) 7.6 2.3

ASCE 7-95

Cate~ory III

Notes to Table 3.4

1 To convert kips to kiioneWlons multiply values by 4.448.

2 This practice does not address wind loads on horizontal vessels.

3 Included in shell loads based on increased diameter.

4 This practice does not address wind loads in the longitudinal direction.

CHAPTER 4RECOMMENDED GUIDELINES

This study shows that the state-of-the-practice for the determination of windloads on industrial structures is quite diverse. In many cases, the publishedtheoretical and experimental work does not address petrochemical or industrial typestructures. Therefore, the committee decided to provide recommended guidelineswith a commentary. The committee has presented the guidelines in a manner suchthat the reader may reevaluate specific items in question.

Note: When used herein, ASCE 7 refers to ASCE 7-95.

GUIDELINE

4.0 GENERAL

Design wind forces for the mainwind force resisting system andcomponents should be determined by theequation

(where F is the applied wind force) usingthe following procedure:

I. A velocity pressure qz is determinedin accordance with the provisions ofSection 6.5 ofASCE 7.

2. The gust effect factor G (or G f) isdetermined in accordance with theprovisions of Table 6-1 and Section 6.6ofASCE 7.

4-1

COMMENTARY

C4.0 GENERAL

The basic equation for design windloading (Equation 4.1) is adopted fromASCE 7 procedures for "Open Buildingsand Other Structures" (ASCE 7 Table 6I). The provisions of Chapter 4 of thisreport primarily provide guidance inselecting appropriate force coefficientsand projected areas.

2. Gf is used in place of G for flexiblestructures, defined by ASCE 7 asstructures with a fundamental frequencyf< I Hz. If the height divided by leasthorizontal dimension is greater than 4,

3, Force coefficients Cr andcorresponding projected areas Af or Aeare determined from the provisions of4, 1,4,2, or 4.3 for pipe racks, openframe structures, and vessels respectively.

4.1 PIPE RACKS

Wind on the pipe rack structure itselfshould be calculated based on noshielding except as described in C4. 1.1.For all structural members Cr = I.8, oralternatively Cr = 2,0 below the first leveland Cr= 1.6 for members above the firstlevel.

4.1.1 Tributary Area for Piping

The tributary area for piping should bebased on the diameter of the largest pipeplus 10% of the width of the pipe rack.This sum is multiplied by the length of thepipes (bent spacing) to determine thetributary area.

4-2

a frequency check may be warranted.

ASCE 7 provides procedures forcomputing gust effect factors in thecommentary section 6.6,

C4.1 PIPE RACKS

The Cr was determined with guidancefrom ASCE 7, Table 6-9 withconsideration of typical solidities aboveand below the first level.

C4.1.1 Tributary Area for Piping

This area is based on the assumptionthat the wind will strike at an angle plusor minus from the horizontal with a slopeof I to 10 and that the largest pipe is onthe windward side. This corresponds toan angle of ±5.7 degrees. In some casesthe pipe rack longitudinal strut or stringermight fall in the shielding envelope andshould be deleted from wind loadconsiderations.

This is a reasoned approach thataccounts for wind on all the pipes (orcable trays) and shielding of the leewardpipes (or cable trays). The basis for theselection is a review ofthe existingpractices. This effect is identified asneeding further research by wind tunneltesting.

:r

4.1.2 Tributary Area for CableTrays

The tributary area for cable traysshould be based on the height of thelargest tray plus 10% ofthe width of thepipe rack. This sum is multiplied by thelength of the trays (bent spacing) todetermine the tributary area.

4.1.3 Force Coefficient for Pipes

The force coefficient Cr = 0.7 should beused as a minimum.

4.1.4 Force Coefficient for CableTrays

For cable trays the force coefficientCF2.0.


4.2.1 General

This section covers wind loads on openframe structures.

Wind loads should be calculated inaccordance with the general proceduresand provisions ofASCE 7 for wind loadson "Other Structures" with theexceptions as noted.

C4.1.2 Tributary Area for CableTrays

See commentary C4.1.1.

C4.1.3 Force Coefficient for Pipes

The force coefficient Cr, for pipe is takenfrom ASCE 7, Table 6-7 for a roundshape, with hID = 25, D.,Jqz > 2.5, and amoderately smooth surface; that is Cr =

0.7. Ifthe largest pipe is insulated, thenconsider using a Cr for a rough pipedependent on the roughness coefficient ofthe insulation (D'!D).

C4.1.4 Force Coefficient for CableTrays

The force coefficient Cr, for cable trays istaken from ASCE 7, Table 6-7 for asquare shape with the face normal to thewind and with hID = 25; that is Cr= 2.0.

4-3

4.2.1.1 Main Wind Force ResistingSystem

I. Wind forces acting on the structuralframe and appurtenances (ladders,handrails, stairs, etc.) should be computedin accordance with 4.2.2.

4-4

C4.2.1.1 Main Wind Force ResistingSystem

I. Alternatively, ladders, handrails andstairs can be treated as equipment insteadof part of the main force resisting frame.

The basic method used to calculatewind loads on an open frame structurewas adapted from a British method forcomputing wind forces on unclad framedbuildings during construction (Willford/Al/sop). That method covers simplethree-dimensional rectangular framestructures with identical, regularly spacedframes in each direction made of sharpedged members. It is based ontheoretical work (Cook) and has beencalibrated against the most extensivewind-tunnel test data available (Georgioll1979). Thus, loads on the structure itselfcan be for a rectangular structure withsimilar frames using the methods ofsection 4.2.

The basic method has been extendedto handle cases such as frames of unequalsolidity, the presence of secondary beams(beams not along column lines), andframes made up of rounded members(Willford/Al/sop,GeorgioulVickery/Church). None ofthe extensions have beenverified experimentally. However, it isstill not unreasonable to presume that fora structure which is not particularlyunusual, irregular, or having too manyappurtenances, the procedures of 4.2

2. \cable 1

struettto theaddedframe

4.2.1.2

Winecompo](excludtrays) sthe procommoareas f(4.1.

4.2.2 1

Desilforce restructurequatio.

md:ade.

ed

:ed

allelf

j

lalns

IT

2. Wind forces on vessels, piping andcable trays located on or attached to thestructure should be calculated accordingto the provisions of 4. 1 and 4.3 andadded to the wind forces acting on theframe in accordance with 4.2.6.

4.2.1.2 Force Coefficients forComponents.

Wind loads for the design of individualcomponents, cladding and appurtenances(excluding vessels, piping and cabletrays) should be calculated according.tothe provisions ofASCE 7. Based oncommon practice force coefficients andareas for several items are given in Table4.1.

4.2.2 Frame Load

Design wind forces for the main windforce resisting system for open framestructures should be determined by theequation:

should yield reasonably reliable windloads for the structure and appurtenancestogether.

2. None of the theoretical orexperimental work published to date hasconsidered the inclusion of random threedimensional solidity (e.g., vessels, heatexchangers, etc.) placed in theframework. However, it is expected thatthe total wind load on equipment will beless than the sum of the loads on theindividual items due to shielding of, andby the frame, and also equipment toequipment shielding.

Thus, the approach taken in 4.2.6 isthe reduction of the total wind load onequipment by a multiplication factor 11 toaccount for this shielding.

C4.2.2 Frame Load

The structure is idealized as two setsof orthogonal frames. The maximumwind force on each set of frames iscalculated independently.

(4.1a) Note: Cr accounts for the entire structurein the direction of the wind.

4-5

TABLE 4.1 Force Coefficients for Wind Loads on Components

Item Cr Projected AreaHandrail 2.0 0.80 Sq ft./itLadder without cage 2.0 0.50 Sq. ft./ft.Ladder with cage 2.0 0.75 SCI. ft./ft.Solid Reetan~es & Flat Plates 2.0Round or Square Shapes See ASCE 7

Table 6-7Stair w/handrail

.

Side elevation 2.0 hand' rail area plus channeldepth

End elevation 2.0 50 % gross area

In Equation 4.1 a F5 is the wind force onstructural frame and appurtenances, qzand G are as defined in 4.0, and

1. The force coefficient Cr is detenninedfrom the provisions of4.2.3.

2. The area of application of force Ae isdetermined per 4.2.5.

3. The design load cases are computedper 4.2.6.

\

(

f

a

u

V

11

4.2.2.1 Limitations of AnalyticalProcedure.

Design wind forces are calculated forthe structure as a whole.

The method is described forstructures which are rectangular in planand elevation.

C4.2.2.1 Limitations of AnalyticalProcedure

No information is provided aboutdistribution ofloads to individual frames.However, it should be noted that thewindward frame will experience a muchlarger percentage of the total wind forcethan any other frames, except possibly forthe case where the solidity ratio of thewindward frame is much less than that ofother frames.

4-6

4.2.3 Force Coefficients

The force coefficient for a set offrames shall be calculated by

Cr= COg / e (4.2)

.where

COg is the force coefficient for the set offrames given in Figure 4.1, and

e is the solidity ratio calculated inaccordance with 4.2.4.

Alternately, Cr may be determinedusing Appendix 4.A

Force coefficients are defined forwind forces acting normal to the framesirrespective of the actual wind direction.

-

C4.2.3 Force Coefficients

Force coefficients COg are obtainedfrom Figure 4.1 (see C4.2.1.1) orAppendix 4.A A single value is obtainedfor each axis of the structure. This valueis the maximum force coefficient for thecomponent of force acting normal to theframes for all horizontal wind angles.Although the wind direction is nominallyconsidered as being normal to the set offrames' under consideration, the maximumforce coefficient occurs when the wind isnot normal to the frames (see C4.2.6.1and 4A.1). The angle at which themaximum force coefficient occurs varieswith the dimensions of the structure, thesolidity, number offrames, and framespacmg.

A method to estimate this angle isgiven in the Appendix 4.A, which alsoprovides Cr values for a larger range ofSF/B and e values than Figure 4.1.

The force coefficients CDg weredeveloped for use on the gross area (i.e.,envelope area) of the structure as used bythe British wind loading standard(Willford/Allsop). These are convertedto force coefficients which are applied tosolid areas as used in ASCE 7 byEquation 4.2.

The force coefficients CDg weredeveloped from wind tunnel tests forstructures with a vertical aspect ratio(ratio of height to width perpendicular tothe flow direction) of four. Although

4-7

Plan View Of Framing

j SF I SF I SF :

I'" ~I '" ~I" ~ I

BNominal Wind ~Direction ,

I'------';E--;E'----I

I I I II I ;E I

I I I I-L-_ I ;E :E I

t ,I

Number of Frames, N

Notes:

(1) Frame spacing ratio is defined as SF/B.

(2) Frame spacing, SF, is measured from centerline to centerline.

(3) Frame width. B, is measured from outside edge to outside edge.

(4) Number of frames, N, is the number of framing lines nonnal to thenominal wind direction (N=4 as shown).

(5) Linear interpolation may be used for values of SF / B not given on thefollowing pages.

Figure 4.1 Force Coefficients, CDg, for Open Frame Structures

4-8

I;;

r

(1) (1)

12

~

x

.~

6

7

'J

II

!O

0.35

f ~.

. f

'i

"i: ,..-.-. tI~~'-t

. T'-'

:--+ . ~ .

0.25 0.30.2

I:

i 'I0.15

"'1'"

Frame Spacing Ratio, Sr/B=0.2

"-'r--"........~.... .... ;

!·_··t·~

;1,iH1Ji' I ~ -

····t··· ....• -. "'-1-'-'"

!: . 1··Too········

!

~.~. ' I. rr tuj

o:r:I'+I)' "j0.1 ~

~

2.51 I ... iii : i : iii I N=

2onCi

U<i

~iJJ 1.50...0c 130~

c:Q}.-u.-it:Q}0

UOJU...0w..

0.5

0.35

3._+

..~....,. "f"! 2l. ..

..+.) ) ···t···

N=

J 12

11

10

9876

5ru++ii 4

0.30.250.20.15

····I·i·li+;

+'1TITT'"

2 I ' ! ! i i I ", i ., ..

1.3

l.5~!!iil lil~~

,-.+..1.-7'"

0.5 n~ I .T.L]ij+ulu~uL mlu.u ": l :: i : i i' :: i i

···t ··-t j j j-_ j j. - i j "-f-'-+"'';'_''-:-'" ····~··_·f ~- ._~_ ..

oil··· ...··Jllliliq!!lilil0.1

onCi

U:of2~

'"'"20c:0~

c".jo..~,8'!)

e.>0

U"-'"-'...0w..

Solidity Ratio, £ Solidity Ratio, £

Figure 4.1 Force Coefficients, C Dg' for Open Frame Structures (cont'd)

o

2

4

'i

7

l)

(,

!O

:I

0.:150.3

-..~ ...

-': "T"

-~_._~_._~... --:-._. '

0.25

~LlllTT

0.2

i:.::.,..r«········

Solidity Ratio, £

...........

.::: ::1 1

...T::t:::LJ.:: :.:t·· .::L·1·'·~ ..-t-- ~ ...+..+.+-:: :: :o ·--·i ·_·i---~--·i··· .... j .... _.. _._j-- -1-· -to

0.1 0.15

o5-rr"""""l~ iii i f 1--+--1--1-.:::::;l;ii!""'~! .... """"

2.5

!Su

'" 2<U

.<<Il<Il0....0t: 1.50-t:

13.s,lu.-::::<U0U

<UU....0u..

\1

10

5

4

7

6

9

0.350.30.2 0.25

Solidity Ratio, £

015

;"r'T"'!" ;.

::I Frame Spacing Ratio, ~fB=0.33

N=j .;; I.....j ......i"r""i...nil31 ' j j . i. 'm, minT: J 12i

1.3

1m

in I···· I .... I .~ I~. I2.5 !!! i ! ! ! ! ! ! :±ir. : ~ , i

:J ••.• jT,. "1 . 'yuc'¥'" '~' '~2 nil nlnL ! ; ,"7, i , , I;>'~, ,~8

\·~jit~prJ4·J..n1~u.:H1. .J : ~: .:,: :~:, ~... ~, .

Ii: 3

. ·.,.·t·; ++.. 2••• <1•••• ,;••• ) •• ,i.._- -_.+._-+... ~ ... ' -....1' ••• ; ••

0.5 , .i!:t:~:;L ::I::::i~',•••• j •• ·i····i····;···· "'-i ···i·· -1"'-+'" ...+_._+- ..~. -+_ .. ····t····~····t "'1'"

........ ····j···j···1····1··· .. _+ .+.+.+.. ··,t···i- -f·· t· .. f- ..~....~ ···f•••• j ••• i __ ; ; ........•...; ~.. _.+. __ .•. .;...•.+ + -··-1· '" ·,·1 ···1··

o iii iii iii iii' j i

0.\

e.uCl

U,;u....

<l::OJ:Vl0....

0t:0~... t:U, ·U-0 6u0Uu~0u..

Figure 4.1 Force Coefficients, C Dg' for Open Frame Structures (cont'd)

,I

4.2.4 Solidity Ratio

The solidity ratio & is given by;

& = As I Ag (4.3)

where Ag is the gross area (envelopearea) ofthe windward frame and As is

the effective solid area of the windwardframe defined by the following •

4.2.4.1 The solid area of a frame isdefined as the solid area of each elementin the plane of the frame projectednormal to the nominal wind direction.Elements considered as part of the solidarea of a frame include beams, columns,bracing, cladding, stairs, ladders,handrails, etc. Items such as vessels,tanks, piping and cable trays are notincluded in calculation of solid area offrame; wind loads on these items arecalculated separately.

4.2.4.2 The presence of flooring ordecking does not cause an increase of the

vertical aspect ratio does not playa largerole in determining overall loads, thecoefficients given in Figure 4. I will likelybe slightly conservative for relativelyshorter structures and slightlyunconservative for relatively tallerstructures

Force coefficients CDg are applicablefor frames consisting of typical sharpedged steel shapes such as wide flangeshapes, channels and angles. ReferenceGeorgioulVickery/Church suggests amethod to account for structurescontaining some members of circular orother cross sectional shape.

C4.2.4 Solidity Ratio

Reference Willjord/AJJsop presentsa method to account for the effects ofsecondary floor beams (beams not in theplane ofa frame). Use ofthis methodmay result in a small increase in the totalwind force on the structure. With theassociated uncertainties with thedetermination of the wind forces thisminor addition may be ignored.

C4.2.4.2 Reference Willjord/AI/sopindicates that although extremely little

4-11

solid area of 424.1 beyond the inclusionof the thickness of the deck.

4.2.4.3 For structures with frames ofequal solidity, the effective solid area As

should be taken as solid area of thewindward frame.

4.2.4.4 For structures where the solidarea ofthe windward frame exceeds thesolid area of the other frames, theeffective solid area As should be taken asthe solid area ofthe windward frame.

4.2.4.5 For structures where the solid. area of the windward frame is less than

the solid area of the other frames, theeffective solid area As should be taken as

the average ofall the frames.

4.2.5 Area of Application of Force

Ae shall be calculated in the same

manner as the effective solid area in 4.2.4except that it is for the portion of thestructure height consistent with thevelocity pressure qz.

experimental work has been doneregarding effects of flooring, the limiteddata available suggest that the presenceof solid decking does not increase windforces above those calculated for the bareframe, and may in fact reduce the loadsdue to a "streamlining" effect. Noresearch relating to open grating floorshas been published. The opinion of thecommittee is that open grating floors willnot significantly affect the wind forces onthe structure

C4.2.4.4 The force coefficients ofFigure 4.1 were developed for sets ofidentical frames. Research shows that thesolidity of the windward frame is themost critical (Cook, Whitbread), leadingto the recommendation. This provision islikely to yield slightly conservative loads,since the greater the solidity of thewindward frame with respect to the otherframes, the greater the shielding of theother frames.

4-12

Ie

tt

tft

c

4

Ps:Ie

dIf

4.2.6 Design Load Cases

The total wind force acting on thestructure in a given direction, FT, is equalto the sum of the wind loads acting onthe structure and appurtenances (Fs),

plus the wind load on the equipment andvessels ( per 4.3), plus the wind load onpiping. See Figure 4.2 for completedefinitions ofFT and Fs

If piping arrangements are not knownthe engineer may assume the piping areato be 10% ofthe gross area of the face ofthe structure for each principal axis. Aforce coefficient of 0.7 should be used forthis piping area.

The following two load cases must beconsidered as a minimum.

4.2.6.1 Frame load + equipment load +piping load (FT) for one axis, actingsimultaneously with 50% of the frameload (Fs) along other "axis, for each

direction. These two combinations areindicated in Figure 4.2.

C4.2.6 Design Load Cases

In some cases this design load willexceed the load which would occur if thestructure were fully clad. It is alsopossible that the wind load on just theframe itself (before equipment loads areadded) will exceed the load on the fullyclad structure. This happens most oftenfor structures with at least 4 to 5 framesand relatively higher solidities Thisphenomenon is very clearly demonstratedin Walshe, which presents forcecoefficients on a building for 10 differentstages of erection, from open frames tothe partially clad to then fully cladbuilding. The wind load on the modelwhen fully clad is less than that duringseveral stages of erection.

C4.2.6.1 While the maximum wind loadnormal to the frame for a structureconsisting of a single frame occurs whenthe wind direction is normal to the planeof the frame, this is not the case for amultiple open framed structure.Maximum load normal to the plane of theframes occurs when the wind direction istypically 10 to 45 degrees from thenormal (Willford/Allsop). This is due tothe fact that for oblique winds there is nodirect shielding of successive columnsand because a larger area of frame isexposed to the wind directly (withoutshielding) as the wind angle increases.Thus the maximum wind load on one set

4-13

Fr

Plan View

r--r--I--;r

I I I I--~... ];--J; ;I--I

I I I IY I--I: ;r--;r

Range of Wind t0.5 FsDirection

Case 1

Plan View

I--;E'---'I ;[

0.5 Fs I I I I--~.. 1--;]; I I

I I I I1--:1:'-----:1::1::-----;[

~~:~ t"Case 2

Notes:

(1) Fs denotes the wind force on the structural frame and appurtenances in theindicated direction (excludes wind load on equipment, piping and cable trays).

(2) FT denotes the total wind force on the structure in the direction indicated,which is the sum of the forces on the structural frame and appurtenances,equipment, and piping. If appropriate, the equipment load may be reduced byconsidering shielding effects per 4.2.6.2.

(3) Load combination factors applied to Fs may alternately be determined by thedetailed method of Appendix 4A and used in place of 0.5 values shown. Thesevalues shall be calculated separately for Case 1 and Case 2.

Figure 4.2 Design Load Cases

4-14

4)1

eedIIn

v

t1.eIIc

r(,(

rt

r

.,

"

4.2.6.2 When, in the engineer'sjudgment, there is substantial shielding ofequipment by the structure or otherequipment on a given level in the winddirection under consideration, the windload on equipment in 4.2.6.1 on that levelmay be reduced by the shielding factor 1'\.

(E+ 8.3)1'\ = (1 - E ) (4-4)

where 1'\ ~ 0.4.

The solidity ratio E is defined in 4.2.4.

1C is the volumetric solidity ratio forthe level under consideration, defined asthe ratio of the sum of the volumes of allequipment, vessels, exchangers, etc. on alevel of the structure to the gross volumeofthe structure at that level.

1C should be taken as 0 when there isno equipment to equipment shielding(e.g., if there is only one exchanger orvessel on the level under consideration,or the equipment is widely spaced).

The wind load on any equipment orportion thereof which extends above thetop ofthe structure shouid not bereduced.

of frames occurs at an angle which willalso induce significant loads on the otherset of frames (WillfordA/lsop,Georgiou/Vickery/Church).

Full and partial loading of structuresgiven in ASCE 7 section 6.8 weredeveloped for clad structures only. Theprovisions of that paragraph are notapplicable to open frame structures dueto the different flow characteristics

C4.2.6.2 These provisions are anattempt by the committee to recognizethe beneficial effects of shielding ofequipment by the structure and otherequipment. The form is very looselybased on shielding equations developedfor sets of trusses, with an additionalfactor introduced to account for thepresence of solid elements.

The factor 1C is used to account forequipment to equipment, and equipmentto structure shielding.

4-]5

4.2.6.3 Horizontal Torsion

Horizontal torsion (torsion about thevertical axis) may be a factor for openframe structures. The engineer shouldconsider the possibility of torsion in thedesign

Consideration should be given to theapplication points ofthe wind load,especially in cases where the buildingframing is irregular and/or equipmentlocations are not symmetric.


Where vessel and piping diameters arespecified, it is intended that insulation, ifpresent, be included in the projected area.Insulation should not be included forstiffness when checking hID for dynamiccharacteristics.

4.3.1 Vertical Vessels

4.3.1.1 Use ASCE 7 to calculatevelocity pressures and to obtain gusteffect factors.

4.3.1.2 Simplified Method

Ifdetailed information (number ofplatforms, platform size, etc.) is unknownat the time of design of thefoundation/piles, the following approachmaybe used:

C4.3 PRESSURE VESSELS

For tall slender vessels, vortexshedding may cause significant oscillatingforce in the crosswind direction. Thismeans that the structure may experiencesignificant loads in both the alongwindand crosswind directions at the sametime. Crosswind forces such as vortexshedding are not addressed in thisdocument.

C.4.3.1.2 Simplified Method

4-16

I(aIIvaa

201

laalm

3d

alCi

Cl

4.

pIIa

I)(0

lfl

dith

2)

1) For the projected width, add 5-ft.(1.52 m) to the diameter of the vessel, oradd 3-ft. (091 m) plus the diameter ofthe largest pipe to the diameter of thevessel, whichever is greater. This willaccount for platforms, ladders, nozzlesand piping below the top tangent line.

2) The vessel height should be increasedone (1) vessel diameter to account for alarge diameter pipe and platform attachedabove the top tangent, as is the case withmost tower arrangements.

3) The increases in vessel height ordiameter to account for wind onappurtenances should not be used incalculating the hID ratio for forcecoefficients or flexibility.

4) The force coefficient (Cr) should bedetermined from ASCE 7, Table 6-7.

4.3.1.3 Detailed Method

If most design detail items (platforms,piping, ladders, etc.) of the vessel areknown, the following method should beused:

I) For the projected width, add 1.5-ft.(0.46 m) to the vessel diameter toaccount for ladders, nozzles and piping 8in. (0.2 m) or smaller and add thediameter of the largest line coming fromthe top portion ofthe vessel.

2) The force coefficient (Cr) should be

1) With limited information on the vesseland appurtenances, this simple approachgives reasonably consistent results.

2) This is an approximation to alleviatethe need for some rather tediouscalculations based on gross assumptions.

3) As noted in 4.3 previously, insulationshould not be included in the hIDcalculations.

4) Any roughness due to nozzles,ladders and other appurtenances iscovered by the increase in diameter.

A moderately smooth surface shouldnormally be assumed. If ribbed insulationwill be used then the D'ID should becalculated.

C4.3.1.3 Detailed Method

This will provide more accuratevalues for foundation design.

I) This is consistent with the valuesmost companies are using.

4-17

taken from ASCE 7, Table 6-7 based onappropriate roughness at vessel surface.

3) For pipes outside the projected widthof the vessel (defined in I) larger than 8in. (0.2 m), including insulation, use theprojected area of the pipe and use a forcecoefficient (Cr) ofO. 7.

For pipes inside the projected width ofthe vessel (defined in I) larger than 8-in.(0.2 m), induding insulation, and morethan 5 pipe diameters from the vesselsurface, add the projected area of thepipe and use a force coefficient (Cr) of0.7.

4) For platforms, use the projected areaofthe support steel and a forcecoefficient (Cr) of2.0.

For handrails use the values for areaand force coefficient from Table 4.1.

Where the railing projects beyond thevessel, the projected area of two (2) setsof railing systems should be used. Afront system and a back system shouldboth be projected.

4.3.2 Horizontal Vessels

4.3.2.1 No check for dynamic propertiesis required.

4.3.2.2 For the projected diameter, add1.5 ft. (0.46 m) to the insulated diameterto account for ladders, nozzles and pipe 8in. (0.2 m) (including insulation) orsmaller.

4.3.2.3 For wind perpendicular to thelong axis of the vessel (transverse wind),the force coefficient (Cr) should bedetermined from ASCE 7, Table 6-7.

3) Cr is determined from ASCE 7, Table6-7 for a moderately smooth surface.

4) The front and back systems of railingsare far enough apart to precludeshielding.

C4.3.2.3 Use BID to determine Crsimilar to 'hID for vertical vessels.

4-18

4.marc(

4.arc(

ar

Sy

4.piC(

4.

4.IS

4.1.tomSli

4.SI

4.marc(

4.3.2.4 For wind in the longitudinaldirection, use Cr ofO.5 for a roundedhead and 1.2 for a flat head.

4.3.2.5 For pipe larger than 8 in. (0.2m), including insulation, use the projectedarea of the pipe and use a forcecoefficient (Cr) of0.7.

4.3.2.6 For platforms, use the projectedarea of the support steel and a forcecoefficient (Cd of2.0.


Use the projected area of each railingsystem.

4.3.2.7 For supports use the actualprojected area. Cr should be 1.3 forconcrete pedestals. For steel supports,use the method described for platforms

4.3.3 Spheres

4.3.3.1 No check for dynamic propertiesis required.

4.3.3.2 For the projected diameter, add1.5 ft. (0.46 m) to the insulated diameterto account for ladders, nozzles and pipe 8in. (0.2 m) (including insulation) orsmaller.

4.3.3.3 Use Cr = 0.5 (for vessel only).Supports should be evaluated separately.

4.3.3.4 For pipe larger than 8 in. (0.2m), including insulation, use the projectedarea of the pipe and use a forcecoefficient (Cr) of 0.7.

C4.3.2.4 This wind direction willseldom control design of foundations.

C4.3.2.6 The reason for projecting thefront and back railing system is that theyare far enough apart to precludeshielding

C4.3.2.7 The 1.3 factor is used becausea pedestal is similar to a bluff rectangularbody.

C4.3.3.3 See ASCE Wind

C4.3.3.4 Cr is determined from ASCE I,Table 6-7 for a moderately smoothsurface.

4-19

4.3.3.5 For platforms, use the projectedarea for the support steel and a forcecoefficient (Cr) of2.0.


Use the projected area of each railingsystem.

4.3.3.6 For supports use the actualprojected area. Cr should be 1.3 forrectangular concrete columns and 0.7 forcircular columns. For steel supports, usethe method described for platforms.

C4.3.3.5 The reason for projecting thefront and back railing system is that theyare far enough apart to precludeshielding.

4-20

APPENDIX 4.AALTERNATE METHOD FOR DETERMINING CF AND LOAD

COMBINAnONS FOR OPEN FRAME STRUCTURES

4A.l BACKGROUND

Maximum wind force nonna! to the face of a rectangular enclosed building occurswhen the wind direction is nonnal to the building face. The same is true for wind load ona singie frame or solid sign. However, this is not the case for an open frame structurewith more than one frame. As the wind direction moves away from the normal and moretowards a quartering wind, columns which once lined up neatly behind each other,shielding each other, become staggered and exposed to the full wind. Additionally, thearea ofthe structure projected on a plane nonnal to the wind also increases.

The variation of the wind loads along each principal axis of a rectangular open framestructure with the direction of wind is shown in Figure 4A 1, for the structure and windangie of attack defined in Figure 4A2. It can readily be seen that when one frame setexperiences its maximum frame load 'A' or D', the frame set along the other axisexperiences a wind force 'C' or 'B' respectively, thus the need for the load combinations ofSection 4.2.6.1. In those provisions, the load at 'C' is roughly estimated to be 50% of 'A'and 'B' is estimated to be 50"/0 of the load at D'. In actuality, the loads on the secondaryaxis can range from about 25% to 75% of the primary axis load, depending on manyfactors including spacing ratio, number of frames, solidity ratio, etc. This appendixprovides a method to obtain a better estimate of the simultaneously acting load on thesecondary axis.

4A.2 FORCE COEFFICIENTS

This method provides force coefficients effor a greater range ofE and SFIB values

than the method of4.2.3, as well as providing an estimate ofUmax. For cases where both

methods are applicable, they will generally yield very similar results. References Nadeemand NadeemlLevitan discuss this method in greater detail. The procedure is as follows:

1. Determine E, SFIB, and N for the principal axis under consideration as per 4.2.4and Figure 4 L

4-21

2. Estimate the wind angle of attack which maximizes the force parallel to the axisunder consideration.

amax = (10 + 58E)0

amax = (16 + 52E tfor 3:<; N :<; 5

for 6:<;N:<; 10

(4Al)

(4A.2)

3. Estimate the force coefficient C[1rom Figure 4A3 by the following procedure:

a) Determine Cf from Figure 4A3(a) for wind angle of attack = amax and

appropriate spacing ratio SF/B,. This Cf is for a structure with N=3 frames

and a solidity ratio ofE=0.1.

b) Determine Cf from Figure 4A.3(b) for a structure with N=3 frames and a

solidity ratio OfE =0.5.

c) Interpolate between results of a) and b) for the actual solidity ratio, yielding aforce coefficient for the correct spacing and solidity ratios, and N=3 frames,CfN=3.,

d) Determine Cf from Figure 4A3(c) for a structure with N=lO frames and a

solidity ratio ofE=0. 1.

e) Determine Cffrom Figure 4A.3(d) for a structure with N=lO frames and a

solidity ratio ofE=0.5.

f) Interpolate between results ofd) and e) for the actual solidity ratio, yielding aforce coefficient for the correct spacing and solidity ratios, and N=10 frames,

CfN=lO .,

g) Determine Cf for the axis under consideration by interpolating between

Ct:N=3 and Cf,N=10 for the actual number offrames

Note that if the structure has exactly 3 or 10 frames, only steps (a-c) or (d-t)respectively need be used. Similarly, if a structure has a solidity ratio verynear to 0.1 or 0.5, only one interpolation between Figures 4A.3(a) and (c) or4A.3(b) and (d) respectively would be necessary.

4A.3 LOAD COMBINAnONS

Section 4.2.6.1 specified the load combination of full wind load on the axis underconsideration acting simultaneously with 50"10 of the frame wind load on the other axis. Amore detailed method to estimate the wind load acting simultaneously on the secondaryaxis frames is given here.

4-22

51

aS<

is

,

a

"

)'Ir

r\.

'I

1. Determine Cf for the principal axis under consideration as per 4.2.3 or 4A.2. Ifprovisions of4.2.3 are used, Umax must still be determined as per 4A.2

2. Determine the force coefficient Cf for the secondary axis from Figure 4A.3, using

E, SF/B, and N values for the secondary axis and a wind angle of attack of (90°

umax). Step 3 in section 4A2 explains how to obtain Cf from Figure 4A3.

4A.4 SAMPLE CALCULAnONS

The proposed method has been used to calculate the force coefficients for astructure whose plan is shown in Figure 4A.4. Summarizing the important frame setproperties,

For winds nominally from west to east(i.e., winds normal to the N-S frame set)

E= 0.136N=4SF 25.4 ft (7.75 m)B = 68.9 ft (21.0 m)SFIB = 25.4 / 68.9 = 0.369

For winds nominally from south to north(i.e., winds normal to the E-W frame set)

E= 0.286N=5SF 16.4 ft (5.0 m)

B = 78.75 ft (24.0 m)SFIB = 16.4 /78.75 = 0.208.

Detennining Force Coefficients: To determine the force coefficient for the E-Wstructural axis (winds nominally normal to the N-S frame), first estimate the wind angle ofattack at which this maximum load will occur. Since N=4 and E= 0.136 for the N-S frameset, Equation 4A 1 yields

Umax= 10+58(0.136)= 18°.

From Figures 4A3(a) and (b), for SF/B = 0.369, Cf= 3.87 and 2.10 for structures

with E = 0.1 and E = 0.5 respectively and N=3 frames. Interpolating between these twovalues for E= 0.136,

Cf,N=3 = 3.87 - [(3.87 - 2.10)/0.4](0.136 - 0.1) =3.71.

4-23

From Figures 4A3(c) and (d), for SFIB = 0.208, Cf = 10.08 and 3.15 for structures

with E = 0.1 and E = 0.5 respectively and 10 frames. Interpolating between these twovalues for E = 0.136,

Ct:N=10 = 10.08 - [(10.08 - 3.15)/0.4](0.136 - 0.1) = 9.46.

Interpolating between the two previous results ofCf,N=3 = 3.71 and Cf,N=IO = 9.46for the case N = 4,

Cf = 3.71 + [(9.46 - 3.71)/7](4 - 3) = 4.53

gives the maximum force coefficient for the N-S set offrames, occurring nearamax= 18°.

Determining Load Combinations: While the maximum wind load is acting on the N-Sset offrames, the wind simultaneously acts on the E-W set of frames at angle of attack of90". 18° = 72°.

The force coefficient for the E-W frames is determined as per step 2 of4A3.For a = 72°, SF/B=O.208 and E = 0.286, interpolation between Figures 4A3(a) and (b)

yields Cf,N=3 = 0.91. Interpolation between Figures 4A3(c) and (d) yields Cf,N=lO =2.84.

One more interpolation between CfN=3 and CfN=10 for N= 5 frames yields Cf =, ,1.46. which is the force coefficient for the wind load acting on the E-W frame set whilethe N-S set is experiencing it's maximum wind load. This combination of loads is shownin Figure 4A5(a).

This entire procedure should now be repeated assuming that maximum wind load actson the E-W set offrames. For this case, amax = 27°, Cf = 4.0 for the E-W frames, with a

simultaneously acting load of Cf = 2.19 for the N-S frame set, as shown in Figure4A5(b).

Note that for the case of full wind load on the E-W axis, use of this alternateprocedure reduced the wind load acting simultaneously on the N-S axis from 50010(4.2.6.2) to 1.46/4.00 = 37%. The load combination for full wind on the N-S structureaxis remained was close to the recommended 50010 at 2. 19/4.53 = 48%.

4-24

es D:,0

"u... A0

"'"-0c::

t6~OJ-0E-

o 15 30 45 60 75 90

-sof

Figure 4A.l Variation of Wind Load vs. Wind Direction

b) N

e on N-S Frame Set

E-W Set of Framesr--------------III,

--» -~.-- .. --. -- .. --.~I -I

~ -ForeIII..

N-S Set of Frames

---.

=

,te%re

ilevn

:ts

la

re

Figure 4A.2 Plan View of Structural Framing

4-25

75

--_Lftoosl........................................ -.... ,-.- ... N = 3-....................................................... .

30 45 60Angle of Attack, aCO)

(b)

i.. ~1B=lorl.• _ •.• L·J.l

j.r ...

I

1:1I I

'·.. J ..r...... j· ...J'.:::::::: ::.::::::...ri"~"T"'I', !

~~I_LI~~=O I 't ' IIiI1.3 .+-•••• --- 1•••••·••· ••.••••••••• 1· --•.•.

0.7~ I I I I I I I I I I I I15

1.1 .1•••••••••+ · ·········1-·· .. ··1··· .. -...•~- - _.•._.•..........•...

O.9-..-.- - -..-----~_ I••.••_.-.·1·---·· .•..•••••••··· ·•···· __ · ···"··············

3.1

2.9

2.7

2.5

'- 2.3u~ 2.1.[)

IE 1.9ClJ0

U

'" 1.7u...0

"'" 1.5

7545 60Angle of Attack, a(O)

(a)

30

3.0

4.0 I .

=i:~j_itlt==jt::LI~ 0 0 I I'3.5+':lr" ."":1:: . _ t·..···j· N = 3

t ,I, ~~:_:J::f::fl:... j...... j

'''j

-!=-F1f=I::=;I, ~ ~i "+I , 1. ,

I;~~.~I~I1Oi~~~ ~~::~~~t::+~I~~:l:0.5' ·1· '1"..·..'[' ·1 + :::::::::: ::::::::1

15 I

,

1.5

'-u..r!.i 2.5[)

IE~u'" 2.0

f' ~N 0a.. "'"

Figure 4A.3 Force Coefficients, C f

,.,(l C

Figure 4A.3 Force Coefficients, C f

--------------------_ .

75

!!1·

45 60Angle of Attack, a(O)

(d)

30

j 1 'I I !:.. "'1 t <: ,/8=0 II ,"1"I ! if-······+·· +1 i \

I 5~ , I , , , I j! I' I

. "j I , i " ,;

IS

2.5

3.5

9.5 i .I. I I

Sr-/8=1.0! I I j I [;]]'.....'1" ----. ,I I I E = 0 5• J I r T ···1 .... .

j iiI I I -8.5;"""1. ·tl L~I. i! t.) ... N -- 10V····t········t·········r··~r i I :, , i

I

7.5

'-u 6.5-5·uIE

CLl 5.5ou8a 4.5r...

756045Angle of Attack, a(O)

(c)

30

·········1···;0-!-

....... "1=

3

t ~.j_.,

..: "':1:::" Sr-/8=O. I .,,....... 7'....... . .

-..... . ··t········· _.,.- ···t··..... . ····t H

... - •••••••• • ..··t . -.- .. '\:.~......~.........+......... . __....•. - .

j i....... . t-········ -... ·····f···· .-..... ...- ·t····· . -- _ ~.... . ................1.. __ . 1. . -.

; !

·..··t·····! .i !······t·· -- + _ .

2-I! i, , I' " ,15

1I -l j ""=i:"

13 I . , .. - -lii-++-+Ie • 0 I I'j 'i- Sr-/8=l.ot"j N = 10..~.!~ j': ·······r········-t·········1····----············

I ! ! i !

.....*~~.!:·:::::·r::::: ..:L:t:·:.\..·····...~~~~ -··t·········L J.. ::~:::,'

t.!:!.:j ! i

-,J. ........•.. ····1 ....,iI --_.,,i·······!! .,··T········,,....j

····l···j

"I"jI .

10+ ..·t··) :-

12

'-U 9..rcv'u 8!Ev0U 7

./:0. 8,N ....'-I 0 6I.I.,

5

4

Figure 4A.3 Force Coefficients, C f (cont'd)

s

Solidity Ratio .. 0.136SIB .0.369

N,.4

N-S frame set.--------

·17S'·9"

outer dimeusionI·

centerline spacing

25'-5' I 25'-5" I 25'-5" E-W frame set• • • • • II ----~-----------.

I Solidity Ratio =0.286

SIB .0.208

N=5

.- ~ ,-.-III

~bIII •b --.1- I

I CIC .I 'Cl

I- ~I

~----_. ~----_.~--:--_. Ie- -t-. ~ '-'-

•'?\c-...

.!: ....u •••Q,'Cl.. -g •

I~....•\c-

Figure 4A.4 Structural Framing Plan for Sample Calculations

F

4-28

]

\.46(37"/0)

4.53

~ 1--+---+---1

_....;iJ:y

(a) Considering Maximum Load on N-S Frame Set

2.19-~:.:.:...- ... "'--+---i---1

(48%)

/,~ t 4.00

/~(b) Considering Maximum Load on E-W Frame Set

s

Figure 4A.5 Force Coefficients, Cr, for Example Design Load Combinations

4-29

CHAPTERSEXAMPLES

This chapter has three appendixes 5.A, 5.B and 5.C will demonstrate theapplication of the recommended guidelines for calculating wind loads on pipe racks,open frame structures, and vessels. The structures considered will be based on theones described in Chapter 3. The structures are located in an assumed petrochemicalplant near Lake Charles, Louisiana (in southwest Louisiana about 20 miles from thecoast).

All calculations are performed using the guidelines from Chapter 4 and theprovisions ofASCE 7-95. Design wind forces for all of the structures are determinedusing the expression

6-16.6.metldetadesi:withseccCon

F=qz GCfA

The velocity pressure qz is determined using Section 6.5 ofASCE 7.

(4.1)

qz = 0.00256 Kz Kzt y2 I (ASCE 7, Eq. 6-1)

The basic wind speed Y is obtained from Figure 6-1 of ASCE 7. For the plantlocation near Lake Charles, Louisiana, Y",120 mph (54 mls). This is a 3-second gustwind speed with an annual probability of exceedence of 0.02 (i.e., mean recurrenceinterval of 50 years).

The importance factor I is obtained from ASCE 7 Table 6-2. For this example animportance factor was chosen based on Category III structures.

The exposure category is selected in accordance with ASCE 7, Section 6.5.3.Exposure C, open terrain with scattered obstructions, was used for this example.Assuming no terrain features such as hills or escarpments are present, the topographicfactor Kzt=l.O per ASCE 7 section 6.5.5. The velocity pressure exposure coefficients

Kz are obtained from ASCE 7, Table 6-3. Velocity pressures are determined using

ASCE 7, Eq. 6-1 shown above. Table 5.1 gives values for qz at several heights.

5-1

theks,thecal:he

:heled

.1 )

-1)

mtJstlce

an

.3.Ie.lie1ts

ng

The gust effect factor G is determined in accordance with the provisions of Table6-1 and Section 6.6 ofASCE 7. For rigid structures, the simplified method of section6.6.1 specifies G=0.85 for structures in terrain exposure C. A more detailed analysismethod for rigid structures is presented in the ASCE 7 Commentary section 6.6. Thisdetailed method is appropriate for very large structures and where more accuracy isdesired. For flexible or dynamically sensitive structures, defined as those structureswith a fundamental frequency f < 1 Hz (i.e., fundamental period of vibration> 1second), Gf is used in place of G. A method to determine Gf is given in ASCE 7Commentary section 6.6.

TABLE 5.1Velocity Pressure Profile for Examples

Height above Ground Velocity Pressurez (ft) Kz qz (pst)

0-15 0.85 36.020 0.90 38.225 0.94 39.830 0.98 41.540 1.04 44.150 1.09 46.260 1.13 47.970 1.17 49.680 1.21 51.390 1.24 52.6100 1.26 53.4120 1.31 55.5140 1.36 57.7160 1.39 58.9

Note: To convert psfto N/m2 multiply values in the table by 47.878.

5-2

APPENDIX S.APIPE RACK EXAMPLE.

The pipe rack cases considered will be as described in Section 3.2, Figure 3.1 andfurther below. Design wind forces are determined by Equation 4.1a (repeated below)where F is the force per unit length of the piping or cable tray:

Design wind pressure, for 30 ft elevation from Table 5.1

(I

Gusteffectfaetor, G=0.85

Force Coefficients

(ASCE 7, Section 6.6.1)

(C

For structural members, Ct = 1.8 or alternatively for structural members above thefirst level Ct = 1.6 and below the first level Ct = 2.0. (Section 4.1)For pipes, Ct=0.7 (Section4.L3)For cable trays, Ct = 2.0 (Section 4.1.4)

Projected Area

Projected Area per foot ofpipe rack, Ae = Largest pipe diameter or cable tray height +10"10 ofthe rack width.

(Sections 4. 11 and 4. 1.2)

SA.! PART I - PIPING AND CABLE TRAY

The guidelines require the consideration ofthe piping or cable tray separately from thestructural members. The following calculations are only for piping or cable trays withoutthe structural support members.

5-3

5

5

•

andlow)

.1)

.1)

.3)

.4)

t-

1.2)

l thelout

Case I - 20 ft (6.10 m) Wide Rack with one (1) - 48 in (1.22 m) Pipe and fourteen(14) -9 in (0.23 m) Pipes

Projected Area, Ae = 4 ft + (20 ft x 0.10) = 6.0 ft2/ft (1.83 m2/m)

Force per foot F =41.5 psfx 0.85 x 0.7 x 6.0 ft2/ft = 148 plf(2.16 kN/m)

Case II - 20 ft (6.10 m) Wide Rack with fifteen (15) - 12 in (0.30 m) Pipes

Projected Area, Ae = 1 ft + (20 ft x 0.10) = 3 ft2/ft (0.92 m2/m)

Force per foot F =41.5 psfx 0.85 x 0.7 x 3.0 ft2/ft= 74 plf(1.08 kN/m)

Case III - 5 ft 6 in (1.68 m) Wide Rack with one (1) - 24 in (0.61 m) pipe and two (2)- 12 in (0.30 m) Pipes

Projected Area, Ae = 2 ft + (55 ft x 0.10) = 2.55 ft2/ft (0.77 m2/m)

Force per foot F = 41.5 psfx 0.85 x 0.7 x 2.55 ft2/ft= 63 plf(0.92 kN/m)

Case IV - 4 ft 6 in (1.37 m) Wide Rack with three (3) - 12 in (0.30 m) Pipes

Projected Area, Ae = 1 ft + (4.5 ft x 0.10) = 1.45 ft2/ft (0.44 m2/m)


Case V - 20 ft (6.10 m) Wide Rack with one (1) - 36 in (0.91 m) Pipe, two (2) - 24 in(0.61 m) Pipes, four (4) - 12 in (0.30 m) Pipes, and six (6) - 9 in (0.23 m) Pipes

Projected Area, Ae = 3 ft + (20 ft x 0.10) = 5.0 If/It (153 m2/m)

Force per foot F =41.5 psfx 0.85 x 0.7 x 5.0 ft2/ft= 123 plf(1.79 kN/m)

Cable Trays- 20 ft (6.10 m) Wide Rack with two (2) - 36 in (0.91) Trays, one (1) - 24in (0.61 m) Tray, two (2)- 18 in (0.46 m) Trays, two (2) - 12 in (0.30 m) Trays, and two(2) - 6 in (0.15 m) all 6 in (0.15 m) high

Projected Area, Ae =05 It + (20 It x 0.10) =2.5 ft2/ft (0.76 m2/m)


5A.2 PART n- STRUCTURAL MEMBERS

For structural members assume the pipe rack geometry is as follows (see Figure5Al):

• 20 It (6.10 m) wide rack with bent spacing on 20 ft (6.10 m) centers all stringers notshielded.

5-4

•

•

•

•

•

•

20' 0'20' 0'- -, .I

j (~I

I I

1I

-, l

1:

PIPE RACK PLAN

Si

HHHOHHH ....

000000000000000

j",..,j

r---:1=o000000000000000'=

;"

N

'--

m

SECTION E3?

FIGURE 5A.! Pipe Rack Example

5-5

j

• The stringer and the columns are assumed to be WI0 and W12 sections respectively.Both stringer and column are assumed to have fireproofing insulation.

• Stringer member projected area per foot ofrack = 1 ft2/ft (0.31 m2/m)• Column projected area per foot ofcolumn = 1.25 ft2/ft (0.38 m2/m)• Three levels ofpipes and cable trays at elevations 18 ft (5.49 m), 24 ft (7.32 m), and

30 ft (9.15 m)• One level of struts at 21 ft (6.40 m)• Conservatively, qz [at elevation 30 ft (9.15 m)] =41.5 psf(1.91 kN/rn2) for all

members.

Next calculate wind loads per bent using a force coefficient Ct = 1.8 for all membersper Section 4.1. Projected area for stringers at elevation 21 ft (6.40 m) is calculated as thesum ofstringers times the stringer depth times the bent spacing.

Projected Area ofStringers = 2 stringers x I ft depth x 20 ft bent spacing= 40 ftl (3.72 ml

)

Similarly the projected area for columns is:

Projected Area ofColumns = 2 columns x 1.25 ft width x 30 ft height = 75 ftl(6.97 ml

)

Total force on the structural members is per Equation 4. 1:

F = qz G Cr Ae =41.5 psfx 0.85 x 1.8 x (40 ftl +75 ftl) = 7300 lbs (32.5 kN)

Alternatively, using Ct = 1.6 for members above the first level and Ct = 2.0 formembers a below the first level.

Projected area for stringers = 40 ft2 (3.72 m2)

Projected area for columns above first level = 2 columns x 1.25 ft x 12 ft high= 30 ft2 (2.79 m2)

Projected area for columns below first level = 2 columns x 1.25 ft x 18 ft high= 45 ft2 (418 m2)

Total force on structure F = 41.5 psfx 0.85 x [(40 ft2 +30 ft2) x 1.6 + 45 ft2 x 2.0]= 71251bs (31.7 kN)

5-6

SA.3 PIPE RACK EXAMPLE - SUMMARY AND CONCLUSION

To combine the effects of the piping, cable tray and the structural members, the piperack structure along with Case V pipes on the bottom leve~ Case II pipes on the middlelev~ and cable trays on the top level are used. See Figure 5A I.

Continued on next page

5-7

Calculate the Total Base Shear using Cr= 1.8 for the structure.

lpedie

Bottom Level ofPipeMiddle Level ofPipeTop Level ofCable TraysStructureTotal Base Shear per bent

123 plfx 20 ft74 plfx 20 ft176 plfx 20 ft

5-8

= 2460 Ibs (11.0 kN)= 1480 Ibs (6.6 kN)= 3520 Ibs (15.7 kN)= 7300 Ibs (32.5 kN)= 14760 Ibs (65.8 kN)

APPENDIX S.BOPEN FRAME EXAMPLE·

The structure considered will be the one described in Section 3.3 and shown inFigures 3.2,3.3 and 3.4. Design wind forces are determined by Equation 4.1a;

It is convenient to determine the velocity pressures at the mid-floor heights and atthe top of the structure. From Table 5.1, qz and Kz are determined and summarized

in Table 5B.l.

TABLE SB.Iqz and K z

Height above Groundz (ft) Kz qz (pst)

10 0.85 36.034 LOO 42.465 LIS 48.8

h= 83 1.22 51.7

Note: To convert psfto N/m2 multiply values in this table by 47.878.

Although the top of the third floor level is at 82 ft, the structure height h wasincreased slightly to account for the handrail and minor equipment on top of thestructure (see Figures. 3.3 and 3.4).

The gust effect factor is determined next. The ratio of height/least horizontaldimension = 83 ft / 41 ft = 2.02 < 4, therefore the structure is not considered aflexible structure. Use G = 0.85, as described at the beginning of Chapter 5.

5-9

5J

c(

arn(c(

tiltharS,thc(T

FI

L

o123

SI

al

fr

fi.

at:d

lS

e

Ua

SB.I ALONG WIND FORCE CALCULATIONS

In order to calculate the force coefficient, the solidity ratio & must first becomputed from Equation 4.3, which stated & = As / Ag. The gross area (or envelopearea) is the area within the outmost projections of the front face normal to thenominal wind direction. Note that the width used below is measured from outsidecolumn face to outside column face. For the wind direction shown in Figure 3.2,

Ag = 83 ft (height) x 41 ft (width) = 3,403 ft2 (316 m2)

To determine the effective solid area, the solid area of the windward frame mustfirst be calculated per 4.2.4.1. In order to facilitate the computation of forces later inthe problem, it is convenient to calculate the solid areas from mid-floor to mid-floor,and sum these to obtain the total solid area of the frame. Member sizes are given inSection 3.3 (except details of handrails and stairs). Calculation of the solid area ofthe windward frame (column line 3) is summarized in Table 5B.2. The stairs wereconsidered as part of the windward frame (see Figure 3.2). The stairs column inTable 5B.2 includes areas of stair stringers, struts, handrails, and bracing.

TABLE5B.2Solid Area of Windward Frame - As

Floor Tributary Solid Areas (ft2)Level Height Cols. Beams Int. Bracing Hand Stairs Total

(ft) Beams Rails0 0-10 30 0 0 19 0 76 125 .1 10-34 72 120 40 40 32 150 4542 34-65 93 60 80 38 40 91 4023 65-83 51 60 40 28 40 17 236

Total Solid Area ofWindward Frame (ft2) = 1217

'113 m2)

Note: To convert ft2 to m2 multiply values in this table by 0.0929.

Since the middle and leeward frames (column lines 2 and I, respectively) aresimilar to the windward frame with the exception of not having stairs. the solid areasand hence the solidity ratios for these two frames will be less than the windwardframe, so As is equal to the solid area of windward frame per 4.2.4.4, which leads to

& = As / Ag = 1,217ft 2 / 3,403 ft2 = 0.358

Next, the coefficient COg is obtained from curves given in Figure 4.1 as a

function of the solidity ratio e, the number of frames N, and the frame spacing ratio

5-10

SF/B· As defined in Figure 4.1, N=3 and SFIB= 20 ft / 41 ft = 0.488. From Figure

4.1, for N=3 and extrapolating slightly for E = 0.358

CDg = 1.09, for SFIB= 0.5CDg = 1.03, for SFIB= 0.33

Interpolating for SFIB= 0.488,CDg = 1.03 + (1.09-1.03)[(.488-.33)/(.5-.33)] = 1.086

Next, the gross area force coefficient CDg is converted into a force coefficientcompatible with ASCE 7 by means ofEquation 4.2.

Cr = CDg /E = 1.086/0.358 = 3.03

The force coefficient could also have been determined directly using the alternatemethod of Appendix 4A. The alternate method is somewhat more time consuming,but it covers a wider range of solidity ratios and frame spacing ratios, and can also beused to determine more accurate load combinations.

The area of application of force Ae has already been determined per floor levelduring calculation of solidity ratio. The wind force transmitted to each floor levelmay now be found by Equation 4-1 a, F = qz GCr Ae as shown below. The total force

on the structural frame and appurtenances Fs is 143.1 kips (639.9 kN), found bysumming the forces at all levels in Table 5B.3.

TABLE5B.3Total Force - Structural Frame and Appurtenances - Fs

Floor qz G Cr Ae F

Level (pst) (fi2) (Ibs)

0 36.0 0.85 3.03 125 11,5901 42.4 0.85 3.03 454 49,5772 48.8 0.85 3.03 402 50,5253 51.7 0.85 3.03 236 31,424

Fs=H= 143,116

Note: To convert pounds force (lbs) to newtons (N) multiply F values in this table by 4.448.

These forces are due to wind acting on the frame only. Wind forces acting on thevessels, equipment and piping are computed in accordance with sections 4.1 and 4.3,and added at the levels where the items are located. The structure supports twohorizontal vessels on floor level one and three horizontal exchangers on floor level

5-11

twwieqde

Eq

VIV2ElE2E3

suj:Taldetabcby!

Not

ves~

= I:5B.1

Ire

mt

lteIg,be

by

8.

he.3,'10

lei

two (see section 3.3 and Figure 3.2). All of these items are subject to transversewind loads for the wind direction under consideration. The projected diameter isequal to the vessel diameter plus 1.5 ft (0.46 m) per 4.3.2.2. The force coefficient isdetennined from ASCE 7 Table 6-7 (per 4.3.2.3). The vessels and exchangers wereassumed to be moderately smooth. These properties are listed in Table 5B.4.

TABLE 5B.4Equipment Properties

Equip Floor Vessel Proj. Dia. Length Proj. Area BID CrLevel Dia. (ft) D (ft) B (ft) Af(ft2)

VI 1 4 5.5 10 55 1.8 0.51V2 1 16 17.5 32 560 1.8 0.51El 2 10 11.5 24 276 2.1 0.52E2 2 10 1l.5 24 276 2.1 0.52E3 2 2 3.5 20 70 5.7 0.58

Note: To convert ft2 to m2 multiply Afvalues in this table by 0.0929.

The wind load on a given vessel or exchanger is the sum of the wind loads on thesupports, platforms, large connecting pipes, and the cylinder itself as summarized inTable 5B.5. This example problem only considers the load on the cylinder. Fordetennining qh, the height of each vessel was assumed to be the mid-floor elevationabove the supporting floor level. A small improvement in accuracy could be obtainedby using the actual top elevation for each piece of equipment.

TABLE5B.5Gross Wind Force - Equipment

Equipment qh G Cr Af F

(pst) (ft2) (Ibs)

VI 42.4 0.85 0.51 55 1011V2 42.4 0.85 0.51 560 10293El 48.8 0.85 0.52 276 5953E2 48.8 0.85 0.52 276 5953E3 48.8 0.85 0.58 70 1684


The projected area of piping and electrical was given as 20% of the projectedvessel area. For example, on floor level one, the piping area is equal to 0.2(55 + 560)

= 123 ft2 (11.42 m2) The wind load on piping per floor level is summarized in Table58.6.

5-12

TABLE 5B.6Gross Wind Force - Piping per Level

Floor qh G Cr Ar F

Level (pst) (ft2) (Ibs)

1 42.4 0.85 0.7 123 31032 48.8 0.85 0.7 124 3612


The total equipment load per floor level is equal to the sum of all of the vessel,exchanger, and piping wind loads on that floor level. For purposes of determining theoverall wind load on the structure, equipment and piping loads can be reduced toaccount for shielding effects (shielding of the equipment by upwind portions of thestructure, shielding of portions of the structure by upwind equipment, and equipmentto equipment shielding). Note that for purposes of designing individual vessels andsupports, the loads should not be reduced.

Since the vessels and exchangers are in the wind shadow of the stairs, diagonalbracing, middle column and intermediate beams, it is appropriate to reduce theequipment load for shielding by the upwind frames. Per equation 4.4, the shieldingfactor 11 is given by

11 = (1- dK + 0.3)

where E = 0.358 as calculated previously. The term K accounts for additionalshielding that equipment provides to other equipment and to downwind frames.

If the additional shielding is considered, then K must be determined for each floorlevel where this additional shielding exists. On floor level one, the smaller vessel VIprovides a limited amount of shielding for the larger vessel V2, and V2 providessignificant shielding for the center column, bracing, and intermediate beam on theleeward frame. The volumetric solidity ratio K is equal to the total volume ofequipment on a floor level divided by the total volume of that floor level (per4.2.6.2).

Equipment volume = 10 1t (42)/4 + 321t (162)/4 = 6560 ft3

Total volume = plan area x height = (40 x 40) x 28 = 44,800 ft3

1( =6560 / 44,800 = 0.15

11 = (I - 0358)(0.15 + 0.3) = 0.82

5-13

ft (I

the

leVIleVIstn:

the

FlolLe~

I

2

5B.

COil

are

side

Thetab!

8.

~l,

~e

to~e

ntId

.alle19

al

)r

'1~s

At the second floor level, exchanger E3 is windward of E 1, but it is very small (2ft (0.61 m) diameter), and exchangers E2 and E3 do not shield a significant portion ofthe leeward frame. Therefore, no additional shielding is appropriate; use 1C = O.

TJ = (I - 0.358l0 + 0.3) = 0.88

Note that if the solidity of the upwind frames varies considerably from level tolevel, and if \( > 0 on any level, it would be appropriate to calculate an I: for eachlevel supporting equipment rather than using a single value of I: for the overallstructure.

Summing the loads on the vessels, exchangers, and piping, per level and applyingthe shielding factors yields the total wind load on equipment seen in Table 5B.7.

TABLE SB.7Total Wind Force - Equipment and Piping

Floor Equipment and Piping Load TJ ReducedLevel Load -lbs (kN)1 V1+V2+piping = 1011+10293+3103 = 0.82 11,814 (52.5)

144071bs (64.1 kN)2 E1+E2+E3+piping = 5953+5953+1684+3612 0.88 15,138 (67.3)

= 17203 lbs (76.5 kN)

Total Equipment Load = ~ Reduced Loads = 26,952 (119.9)

SB.2 CROSSWIND FORCE CALCULATIONS

The next step is to repeat the analysis for the nominal wind direction normal tocolumn line A (see Figures 3.2 and 3.4) - "non windward" frame. The member sizesare the same on this elevation except that the intermediate beams are WI O's and

erBeams EI 20 ft 0 inBeams EI 48 ft 0 inBeams EI 82 ft 0 in

- WI4- WI6- WI2

The gross area of the windward face includes the stair tower on the right handside of the structure.

Ag = (83 x 41) + (9 x 49) = 3,844 ft2

The solid areas for the windward frame are given below. The stairs column in thetable includes areas of stair column, struts, and handrails (See Table 5B.8).

5-14

TABLE5B.8Solid Area - As

Floor Tributary Solid Areas (ft2)Level Height Cols. Beams Int. Bracing Hand Stairs Total

(fi) Beams Rails0 0-10 30 0 0 19 0 24 731 10-34 72 46 8 35 40 44 2452 34-65 93 53 41 36 40 36 2993 65-83 51 40 0 16 40 0 147

Total Solid Area ofWindward Frame (fi2) = 764

Note: To convert ft2 to m2 multiply As values in this table by 0.0929.

Since the solidity of neither the middle and leeward frames (column lines B and C,respectively) exceeds that of the windward frame, As is equal to the solid area ofwindward frame, yielding

e = As / Ag = 764 ft 2 / 3,844 ft2 = 0.199

The frame spacing ratio in this direction is SF/B= 20 ft / 46 ft = 0.435. Since thewidth is not uniform (the stair tower stops at the second floor level), an average valueofB was used. From Figure 4.1 for N=3 and e = 0 199

COg =0.72, for SF/B= 0.5

COg = 0.71, for SF/B= 0.33

Therefore use COg = 0.716.

Cr= COg Ie = 0.716/0.199 = 3.60

The wind forces per floor level are shown in Table 5B.9.

The wind direction is parallel to the axis of the vessels and exchangers(longitudinal wind). The vessels have rounded heads and the exchangers have flatheads. Force coefficients for this case are given in 4.3.2.4, and the wind loads aretabulated in Table 5B.I0.

5-15

F

f(

.e

'sIt'e

TABLE 5B.9Total Force - Structural Frame and Appurtenances - Fs

Floor qz G Cr Ae F

Level (pst) (ft2) (lbs)

0 36.0 0.85 3.60 73 8,0421 42.4 0.85 3.60 245 31,7872 48.8 0.85 3.60 299 44,6493 51.7 0.85 3.60 147 23,256

Fs="EF= 107,734

Note: To convert pounds force (Ibs) to newtons (N) multiply F values in this table by 4.448.

TABLE 5B.I0Gross Wind Force - Equipment

Equipment qh G Cr Af F

(pst) (ft2) (lbs)

VI 42.4 0.85 0.5 13 226V2 42.4 0.85 0.5 201 3624E1 48.8 0.85 1.2 79 3910E2 48.8 0.85 1.2 79 3910E3 48.8 0.85 1.2 3 156

Note: To convert pounds force (Ibs) to newtons (N) multiply F values in this table by 4.448.

The wind load in the piping and electrical is the same as calculated previously.For this wind direction, there is no significant shielding of the equipment by thewindward frame and no equipment to equipment shielding, so no reduction is takenon equipment load. Summing the loads on the vessels, exchangers, and piping perlevel yields

Levell: VI+V2+piping=226+3624+3103 = 6,953Ibs(30.9kN)

Level 2: EI + E2 + E3 + piping = 3910 + 3910 + 156 + 3612 = 11,5881bs(51.5 kN)

for a total equipment and piping load ofFE= 18,540 lbs (82.5 kN).

5-16

5B.3 Open Frame Example - Summary and Conclusion

The results thus far are summarized in the Table 58.11. The load combinationsfor design are application of FT in one direction simultaneously with 0.5 Fs in theother, per 4.2.6.1. These combinations are shown in Figure 58. 1(a).

TABLE 5B.11Summary

Wind - Direction 1 Wind - Direction 2Wind Load on Structural Frame Fs 143 kips (636 kN) 108 kips (480 kN)

Wind Load on Equipment and FE 27 kips (120 kN) 19 kips (84.5 kN)Piping

Total Wind Load on Structure FT 170 kips (756 kN) 127 kips (565 kN)

Using the alternate method of Appendix 4A to solve this entire problem, the forcecoefficient for the first wind direction would be 2.92 instead of 3.03. The forcecoefficient for the second wind direction would be 3.44 instead of 3.60. Wind loadon equipment is unaffected. The load combination factor on Fs for load case Iwould be 0.58 instead of 0.5, and the factor on Fs for load case 2 would be 0.41instead of 0.5. The wind loads obtained using the alternate method are shown inFigures 5B.l(b).

5-17

Plan View Plan View

I :I I I :E I 0.5 Fs = 72 kipsFT=170kips

I I I (756 kN) I I I (320 kN)

:I 1 ;[-1 dIIII: :I I ;[-1 dIIII:

I I I I I I I II :E I-I I :E I-I

t%geOfWiDd

t ~Direction

0.5 F. = 54 kips FT= 127 kips(240 kN) (565 kN)

Gase 1 Gase2

(a) Using method in guidelines

:I :I I I;- = 165 kips I I I 0.41 Fa = 57 kips

I I I I I I(734 kN) (254 kN):I :I I---J: .. I I I-3: ill

I I I I I I I I:I :I I-I:

~I I I-3:

t t l'0.58 F. = 60 kips FT= 122 kips

(267 kN) (543 kN)Case 1 Case 2

(b) Using method of Appendix 4A

Figure 5B.l Design Load Cases for Open Frame Example

5-18

APPENDIX S.CPRESSURE VESSELS EXAMPLE

This section will demonstrate the application of the recommended guidelines forcala.ilating wind loads on pressure vessels. Both the vertical and the horizontal vesselsdescribed in Section 3.4 and shown in Figures 3.S and 3.6 will be considered.

SC.t VERTICAL VESSEL

SC.l.1 Simplified Method - Rigid Vessel

Wmd loads determined using Equation 4.1a; F = qzGCr Ae; are shown in Table

Sc.1. The velocity pressure, qz is determined from Table S.1. Other terms in equation

4.1a are determined as follows:

G=0.8S

hID = ISO/IO = IS

Assume vessel is moderately smooth, therefore

Ct= 0.6 + 8xO.1/18 = 0.64

Increased diameter to approximate appurtenances:

D + S ft. = 10 + S = IS ft. orD + 3 ft. + dia. oflargest pipe = 10 + 3 + 1.5 = 14.S ft.Largest controls, therefore, effective D = IS ft. (4.S7 m)

Therefore, Ae = ISh


(ASCE 7, Table 6-7)

(Section 4.3.1.2)

•

•

5

4

Height increase to account for platform and vapor line above tangent line is Idiameter, which is 10 ft. per section 4.3.1.2. Therefore total effective height of thestructure is 160 ft. (48.77 m).

S-19

)rIs

e

n

)

TABLE SC.lSimplified Method - Calculation of Base Shear

Ht. Above Ground qipst) G Cr Ae (fe) F (Ibs)

0- 15 36.0 0.85 0.64 225 4400

15 - 20 37.1 0.85 0.64 75 1500

20 - 40 41.5 0.85 0.64 300 6800

40 - 60 46.2 0.85 0.64 300 7500

60 - 80 49.6 0.85 0.64 300 8100

80 - 100 52.6 0.85 0.64 300 8600

100 - 120 54.5 0.85 0.64 300 8900

120 - 140 56.6 0.85 0.64 300 9200

140 - 160 58.3 0.85 0.64 300 9500

Total = 64,500 Ibs. (287 kN)

SC.l.2 Detailed Method - Rigid Vessel

SC.l.2.1 Vessel + MisceUaneous


5C.2. The velocity pressure, qz is determined from Table 5.1. Other terms in equation

4.1 a are determined as follows:)

) G=0.85

hID = 150/10 = 15

Assume vessel is moderately smooth, therefore

Cr= 0.6 + 8xO.1/18 = 0.64


(-ASCE 7, Table 6-7)

1e

Increased diameter to approximate ladder, nozzles & piping 8" or smaUer:

D + 1.5 ft. = 10 + 1.5 = 11.5 ft. (3.51 m)

5-20

(Section 4.3.1.3)

Therefore, Ae = l1.5h

TABLE SC.2Detailed Method -Vessel & Miscellaneous - Calculation of Base Shear

Ht. Above Ground qz<psf) G Cr Ae F (Ibs)(ft2)

0- 15 36.0 0.85 0.64 172..5 3400

15 - 20 37.1 0.85 0.64 57.5 1200

20 - 40 41.5 0.85 0.64 230 5200

40- 60 46.2 0.85 0.64 230 5800

60 - 80 49.6 0.85 0.64 230 6200

80 - 100 52.6 0.85 0.64 230 6600

100 - 120 54.5 0.85 0.64 230 6800

120 - 140 56.6 0.85 0.64 230 7100

140 - 150 58.0 0.85 0.64 115 3600

Total = 45,900 Ibs. (204 kN)

SC.l.2.2 Pipe:


5C.3. The velocity pressure, qz is determined from Table 5.1. Other terms in equation

4.1a are determined as follows:

L

G=0.85

Cr=0.7

Pipe dia. = 18" = 1.5 ft. (0.46 m)


(Section 4.3.1.3)

Therefore, Ae = 1.5h (except for the curved section above El. 150 which must be

calculated separately - see Figure 3.5)

Ae above El. 150 = 3.14 x 10/2 x 1.5 = 24 ft2 (2.2 m2) -

5-21

{Note - the pipe starts atEl. 15.0 (see Figure 3.5)}

j

N)

TABLE SC.3Detailed Method -Pipe - Calculation of Base Shear

Ht. Above Ground qz G Cr Ae F (lbs)

(pst) (fe)

15 - 20 37.1 0.85 0.70 8 180

20- 40 41.7 0.85 0.70 30 740

40-60 46.2 0.85 0.70 30 820

60 - 80 49.6 0.85 0.70 30 890

80 -100 52.6 0.85 0.70 30 940

100 - 120 54.5 0.85 0.70 30 970

120 - 140 56.6 0.85 0.70 30 IOlO

140 - 150 58.0 0.85 0.70 15 520

150 - 155 58.5 0.85 0.70 24 840

Total = 6,900 Ibs. (30.7 kN)

SC.l.2.3 Platforms (Refer to Figure 3.5)

The platform at EI. 150 Gust above the top ofthe vessel) is a square platform 12 ft. x12 ft. in plan with handrail around the perimeter. It is assumed that the platform structuralframing will be 8-inches deep (8"/12" = 0.70 sq. ft.l1in. ft.).

>nTherefore, Ae (plat. fram.) = 0.7 x 12 = 8.4 ft2

Ae (front handrail) = 0.8 x 12 = 9.6 ft. 2

Ae (back handrail) = 0.8 x 12 = 9.6 ft227.6 ft2 (2.56 m2

)

qz= 58.3 psf

(Table 4.1)

(Section 4.3.1.3)

(Table 5.1)

G=0.85

Cr = 2.0


(Section 4.3.1.3)

It

}

F = qzGCr Ae = 58.3 x 0.85 x 2.0 x 27.6 = 2700 Ibs (12.0 kN)

5-22

The other platforms are circular and extend 3 ft. beyond the outside radius of thevessel. Therefore the radial distance (R) from the centerline of the vessel to the outside ofthe platform is 5 + 3 = 8 ft. (2.44 m). The angle (60°,90° and 180') shown on Figure 3.5is the angle subtended by the ends of the platform as measured at the centerline of thevessel. Therefore, the projected length of the platform is calculated by the equation:

L = 2RSin(subtended anglel2)

Platform at El. 100 ft. - subtended angle = 60°

Projected length = 2 x 8 x Sin (60/2) = 8.0 ft.

Assume platform framing is 6-in. deep (0.5 sq.ft.llin.ft.)

Ae (plat. fram.) = 0.5 x 8.0 =

Ae (handrail) = 0.8 x 8.0 =

qz = 53.4 psf

G=0.85

Cr=2.0

4.0 ft2

6.4 ft2

10.4 ft2 (0.97 m2)

(Table 4.1)

(Table 5.1)


(Section 4.3.1.3)

F = qzGCr Ae = 53.4 x 0.85 x 2.0 x 10.4 = 940 Ibs. (4.2 kN)

Platform at El. 75 ft. - subtended angle = 60°

Projected length = 2 x 8 x Sin (60/2) = 8.0 ft.

Assume platform framing is 6-in. deep (0.5 sq.ft./Iin.ft.)

Ae (plat. fram.) =

Ae (handrail) =

qz = 50.5 psf

G=0.85

Cr=2.0

0.5 x 8.0 = 4.0 ft2

0.8 x 8.0 = 6.4 ft2

10.4 ft2 (0.97 m2)

(Table 4.1)

(TableS. I)


(Section 4.3.1.3)

F = qzGCr Ae = 50.5 x 0.85 x 2.0 x 10.4 = 890 Ibs. (4.0 kN)

5-23

Platfonn at EL 45 ft. - subtended angle = 90°

Projected length = 2 x 8 x Sin (90/2) = 11.3 ft. Since the projected length is largerthan the vessel diameter, the back handrail will be included (Section 4.3.1.3). Backhandrail projected length = 3 ft. x Sin 45° x 2 sides = 4.2 ft

Assume platfonn framing is 6-in. deep (0.5 sq.ft./lin.ft.)

)

Ae (plat. fram.) = 0.5 x 11.3 = 5.7 ft?Ae (front handrail) = 0.8 x 11.3 = 9.0 ft?Ae (back handrail) = 0.8 x 4.2 = 3.3 ft. 2

18.0 ft2 (1.67 m2)

qz =45.2 psf

G=0.85

C f =2.0

(Table 4.1)

(Section 4.3.1.3)

(Table 5.1)


(Section 4.3.1.3)

F = qZGC f Ae = 45.2 x 0.85 x 2.0 x 18.0 = 1380 lbs. (6.2 kN)

Platfonn at El. 15 ft. - subtended angle = 1800

Projected length = 2 x 8 x Sin (180/2) = 16 ft. Since the projected length is larger thatthe vessel diameter, the back handrail will be included (Section 4.3.1.3). Backhandrail projected length = 3 ft. x Sin 90° x 2 sides = 6 ft.

Assume Platfonn framing is 6-in. deep (0.5 sq.ft.llin.ft.)

Ae (plat. fram.) =

Ae (front handrail) =

Ae (back handrail) =

qz = 36.0 psf

G=0.85

Cf =20

0.5 x 16.0 =

0.8x 16.0 =

0.8 x6.0 =

8.0 ft2

12.8 ft2

4.8 ft225.6 ft2 (2.38 m2 )

(Table 4.1)

(Section 4.3.1.3)

(Table 5.1)


(Section 4.3.1.3)

F = qzGCrAe = 36.0 x 0.85 x 2.0 x 25.6 = 1570 Ibs. (7.0 kN)

5-24

Total shear on platforms = 2700 + 940 + 890 + 1380 + 1570 = 7480 lbs (33.3 kN)

Total shear on foundation:

Vessel & MiscellaneousPipePlatformsTotal

= 45,900 lbs= 6,9001bs= 7.4801bs= 60,280 Ibs (268 kN)

SC.1.3 Analysis of Flexible Vessels

The only difference between loads resulting from the analysis of the vessel as"Flexible" vs "Rigid" is that "Gr" (the gust response factor for main wind-force resistingsystems of flexible buildings and structures) is substituted for "G" in the rigid analysis.ASCE 7-95, Section 6.6 states that Gr shall be calculated by a rational analysis thatincorporates the dynamic properties of the main wind-force resisting system. A method isprovided in the commentary. However, various companies and individuals havedeveloped their own "rational" analysis. Ifone chooses to compare the numbers betweenrigid and flexible in Table 3.3, one will find that the factors are not consistent between thevarious Design Practices. Comparison of procedures for flexible structures is beyond thescope ofthis report. Therefore, no attempt has been made to make the factors agree.

For the "Recommended" methods, the procedure outlined in ASCE 7-95 Commentary,section 6.6 was utilized to detennine Gr = 1.03

• SIMPLIFIED (FLEXIBLE):

TotalShear= (Gr/G)x64,500= (l.03 /0.85) x 64,500 = 78,200 lbs (348 kN)

• DETAILED (FLEXIBLE):

Vessel + Misc.:Shear = (Gr/G) x 45,900 Ibs

= (1.03/085) x 45,900 =

Pipe:Shear =(Gr/ G) x 6900 Ibs

= (1.03 /0.85) x 6900 =

55,6001bs

8,4001bs

5-25

Platfonns:Shear =(Grl G) x 7480lbs

= (103 10.85) x 7480 =

Total =

..2.l00 Ibs73,100 lbs (325 kN)

SC.2 HORIZONTAL VESSELS - (Refer to Figure 3.6)

SC.2.1 Transverse Wind (wind on the side of the vessel)

(Equation 4.1a; Ae is defined in Section 4.2.5)

h = 20 ft. at platform leve~ qz = 38.2 psf

SC.2.1.1 Vessel + Miscellaneous

G=0.85

(See Table 5.1)


BID = 50/12 = 4.2, assume vessel is moderately smooth, therefore

Cr= 0.5 + 3.2 x 0.1/6 = 0.55 (ASCE 7, Table 6-7)

Increased Diameter to approximate ladder, nozzles & piping 8" or smaller:D + 1.5 ft. = 12 + 1.5 = 13.5 ft. (4.1 m) (Section 4.3.2.2)

Therefore, Ae = 13.5 x 54 avg. = 729 ft.2 (67.7 rn2)

Calculate Shear at Base:

F = qzGCr Ae = 38.2 x 0.85 x 0.55 x 729 = 13,000 Ibs (57.8 kN)

SC.2.1.2 Platfonn:

The platform is a rectangular platform 10 ft. x 30 ft. in plan with handrail around theperimeter. It is assumed that the platform structural framing will be IO-inches deep(10"/12" = 0.8 sq. ft./Iin. ft.).

Therefore, Ae (plat. fram.)

Ae (front handrail)

Ae (back handrail)

qz = 38.2 psf

= 0.8 x 30 = 24.0 ft.2

= 0.8 x 30 = 24.0 ft2

= 0.8 x 30 = 24.0 ft2

72.0 ft.2 (6.7 m2)

5-26

(Table 4.1)

(Section 4.3.2.6)

(Table 5.1)

G=0.85

Cr= 2.0


(Section 4.3.2.6)


SC.2.1.3 Supports

Steel saddle

Ae = 0.5 x 2.0 x 2 (supports) = 2.0 ft2 (0.2 m2)

qz = 38.2 psf (TableS. I)

G=0.85

Cr= 2.0


Concrete support:


qz=38.2psf

G=0.85

Cr=1.3


SC.2.1.4 Total Shear, Transverse Wind


(Section 4.3.2.7)

(Table 5.1)


(Section 4.3.2.7)

SC.2.2 Longitudinal Wind (wind on the end of the vessel)

Vessel & MiscellaneousPlatfonnSupports (steel)Supports (concrete)Total

= 13,000 lbs= 4,700 Ibs= 1301bs= 340lbs= 18,170 Ibs. (80.8 kN)

j5-27

1)

5)

Ij,

h = 20 ft. at platfonn level, qz = 38.2 psf

SC2.2.1 Vessel + Miscellaneous

G=0.85

Elliptical head, therefore Cr = 0.5

(See Table 5.1)


(Section 43.2.4)

Increased diameter to approximate ladder, nozzles & piping 8" or smaller:

) D + 1.5 ft. = 12 + 1.5 = 13.5 ft. (4.1 m)

Therefore, Ae = 3.14 x 13.5 x 13.5/4 = 143.1 ft.2 (13.3 m2)

Calculate shear at base:

F =qzGCrAe=38.2xO.85 x 0.5 x 143.1 =2320 Ibs (10.3 kN)

SC2.2.2 Platform:

(Section 4.3.2.2)

The platfonn is a rectangular platfonn lOft. x 30 ft. in plan with handrail around theperimeter. It is assumed that the platfonn structural framing will be 10-inches deep(10"/12" = 0.8 sq. ft./lin. ft.).I Therefore, Ae (plat. fram.)

Ae (front handrail)

Ae (back handrail)

qz = 38.2 psf

G=0.85

Cr= 2.0

=0.8x 1O=8.0ft2

=0.8x 10=8.0ft2

= 0.8 x 10 = 8.0 ft. 2

24.0 ft2 (2.2 m2)

(Table '4. I)

(Section 4.3.2.6)

(Table 5.1)


(Section 4.3.2.6)

F = qzGCr Ae = 38.2 x 0.85 x 2.0 x 24.0 = 1560 lbs (6.9 kN)

SC2.2.3 Supports

Steel saddle - 10 ft. wide x 3 ft. (avg.) high

Ae = 100 x 3.0 x 2 (supports) = 60.0 ft2 (5.6 m2)

5-28

qz = 38.2 psf

G=0.85

Cr=2.0

(Table 5.1)


(Section 4.3.2.7)

F = qzGCr Ae = 38.2 x 0.85 x 2.0 x 60.0 = 3900 lbs (17.3 kN)

Concrete support· 11 ft. wide x 4 ft. high


qz=38.2 psf (Table 5.1)6.1


SC.2.2.4 Total Shear, Longitudinal Wind

G=0.85

Cr=1.3

Vessel & MiscellaneousPlatformSupports (steel)Supports (concrete)Total

= 2,320 lbs= 1,560 lbs= 3,900 lbs= 3.710 lbs=11,490 lbs. (51.1 kN)

5-29


(Section 4.3.2.7)

II

1

litlinpi:

tyll(

thet

tl

vv

Br

rIi

CHAPTER6·RESEARCH NEEDS

6.0 GENERAL

To date, limited research has been conducted (or at least reported in the openliterature) specifically related to wind loads on the types of industrial structures addressedin this report. The standards process requires that provisions be based on published,peer-reviewed research findings. This fact, in part, explains why pipe racks and mosttypes of open frame structures and vessels found in the process industries are notaddressed in ASCE 7. The lack of guidance from wind loading codes and standards andthe absence of specific information in the technical literature has forced practicingengineers to make many assumptions and extrapolations far beyond the intended scope ofthe code and standard provisions, extrapolations often based on experience and engineering judgment alone. Differences in experience and judgment are manifested in thevariety of procedures used by different firms and the sometimes accompanying largevariations in estimated loads, as documented in Chapters 2 and 3 ofthis report.

It is understandable that the significant differences mentioned above could occur,given that the true nature of wind-structure interaction is often highly nonlinear andnonintuitive. In these cases, extrapolation beyond the boundaries of what is understood isa sometimes risky, but nonetheless necessary, venture. The recommendations set forth inChapter 4 are based as much as possible on the solid foundation provided by ASCE 7.Beyond that, guidelines were based on the limited research data available, the current stateofengineering practice, and the combined experience and judgment of the members of theWmd Induced Forces Task Committee. At least as important as the provisions of therecommended guidelines is the material contained in the commentary sections, whichwhenever possible gives the basis, rationale, and limitations for the guidelines.

The foregoing discussion clearly points out the need for research on wind effects onindustrial structures. Results of the comparative study and the investigation of availableresearch data (or lack thereot) for the different structure types were used to identify andprioritize some ofthe most important questions which need to be answered.

6-1

In an overall sense, piperack structures exhibited the greatest vanatIon in loadsbetween design guides of different companies and the greatest uncertainty in developing aconsensus method for analysis. The committee feels that piperack structures in generalshould have the highest priority in any research program. Some specific items of concerninclude: determining appropriate force coefficients for pipes in a piperack structure;investigation of shielding and effects ofdifferent sizes of pipes together on the same level;force coefficients and shielding behavior of cable trays in a piperack; and investigation of\vind loads on a vertical row of pipes, with \vind direction ranging from parallel toperpendicular to the row.

Open frame structures were the next greatest cause of concern, with base shears onthe structure used in the comparative study varying from highest to lowest by a factor oftwo. Wmd turmel test results on models simulating the steel franting alone are availableand were used in developing the guidelines presented in Chapter 4, but no data areavailable on the effects of equipment and piping within the steel frames. Some criticalquestions to be answered for open frame structures include: Is there an upper bound onthe load, and if so, what is it? What are the effects of equipment and vessels within thestructure? Does solid or open flooring affect the loads?

Although some vessel loads also varied significantly from company to company,vessels were given the lowest overall priority, perhaps because the general procedures forcalculating these loads were fairly similar. All finns used force coefficients for the basicshapes from ASCE 7-88 Table 12, differing primarily in treatment of surface roughnessand projected areas to use. Specific questions which need to be answered includeinvestigating the effects of platforms, large vertical pipes and smaller obstructions such asnozzles, ladders and small pipes.

6.1 RESEARCH PRIORITIES

Discussions among the committee led to the following prioritized list of the mostsignificant unanswered research questions as:

I. What are appropriate force coefficients and shielding effects for pipes m apip~rack structure?

2. What are appropriate force coefficients and shielding effects for cable trays in apiperack structure?

3. Is there an of the upper bound for wind induced forces on open frame structuresthat are rectangular in shape? If so, how is it determined?

4. What are the effects of 3D bluffbodies (equipment and vessels) in an open framestructure?

6-2

ds:a:alm"e;~l;

ofto

m)fIe"eilln.e

"

5

T

5. What are the loads on vertical rows ofpipes (force coefficients for wind directionsfrom perpendicular to parallel to a row)?

6. What force coefficients should be used for different size, type and orientation ofplatforms on a vessel?

7. What are the wind load interactions between a large vertical pipe and a verticalvessel?

8. What are appropriate force coefficients for ladders, nozzles and small pipes on avessel? Can these items be accounted for 'by a simple increase in vessel diameteras proposed in Chapter 4 recommendations?

9. Do flooring and interior framing significantly affect loads on open framestructures? If so, how?

10. What are the effects of irregular (nonreetangular) plan view open framestructures on the magnitude and application of the wind induced force?

11. What is the wind environment in a large petrochemical or energy facility?Does it significantly affect the wind loads?

6-3

p

p~

(

~

a:

Fa

NOMENCLATURE

area of application of force for the portion of the structure height consistent with the

velocity pressure qz' in square feet;

area of other structures or components and cladding thereof projected on a plane normal

to wind direction, in square feet;gross area of windward frame, in square feet;effective solid area of windward frame, in square feet;frame width or horizontal vessel length, in feet;force coefficient for a set of frames, applicable to gross (envelope) area ofthe frames;force coefficient;outside diameter of circular pipe or vessel, in feet;depth of protruding elements (ribs or spoilers), in feet;design wind force, in pounds;gust effect factor for main wind-force resisting systems of rigid structures,(ASCE 7 -95);gust response factor for main wind-force resisting systems of flexible buildings andstructures (ASCE 7-93 and previous versions);gust effect factor for main wind-force resisting systems of flexible buildings andstructures (ASCE 7-95);gust response factor for main wind-force resisting systems of rigid structures evaluatedat height z = h (ASCE 7-93 and previous versions);height of structure or vessel, in feet;importance factor;velocity pressure exposure coefficient evaluated at height z;

topographic factor;

number of frames;velocity pressure evaluated at height z above ground, in pounds per square feet;

frame spacing, in feet;basic wind speed, in miles per hour;height above ground, in feet;ratio ofeffective solid area of windward frame to gross area of windward frame;volumetric solidity ratio for the floor level under consideration. Defined as the ratio ofthe sum of the volumes ofall equipment, vessels, exchangers, etc. on a level to the grossvolume of that level;

= a reduction factor to account for shielding ofequipment by the structure and shielding ofequipment by equipment;

Ae =

Af =

Ag =As =B =COg =Cf =D =D' =F =G =

G =

Gf =

Gh =

h =I =Kz =

Kzt =N =qz =

SF =V =z =g =K =

A-I

th the

lormal

es;

:s and

s and

luated

Itio ofgross

jng of

GLOSSARY

Open Frame Structure - Open frame structures support equipment and plpmgwithin an open structural frame unenclosed by siding or other shieldingappurtenances.

Pipe Rack - An open frame structure whose primary purpose is the support ofpiping and cable trays. Pipe racks are normal1y 15 ft to 25 ft (45.7m to 76.2m) inwidth and have two (2) or more levels.

Pressure Vessel- A container usually cylindrical in shape containing of a gasand/or liquid under pressure.

B-1

REFERENCES

Willford/Allsop Willford, M. R., and Allsop, A C, "Design Guide for Wind Loadson Unclad Framed Building Structures During ConstnJction:Supplement 3 to The Designer's Guide to Wind Loading ofBuilding Structures," Building Research Establishment Report,Garston, UK, 1990.

Cook Cook, N. 1., "The Designer's Guide to Wind Loading ofBuildingStructures Part 2: Static Structures," Butterworths, London,1990.

Georgiou Georgiou, P. N., "Wind Loads on Building Frames" M.E.Sc. Thesis,University of Western Ontario, Canada, 1979.

GeorgiouNickery/Church, Georgiou, P. N.; Vickery, B. J.; and Church, R, "WindLoading on Open Framed Structures," Program and WorkshopNotes, CWOWE III: Third Canadian Workshop on WindEngineering, Vancouver, April, 1981, Vll pp. 1-19.

Whitbread

Walshe

ASCE Wind

Nadeem

Whitbread, R. E., "The Influence ofShielding on the Wind ForcesExperienced by Arrays of Lattice Frames" Wind Engineering:Proceedings of the Fifth International Conference on WindEngineering (Fort Collins, Colorado, USA, July, 1979), J. E.Cermak, Ed., Pergamon Press, 1980, pp. 405-420.

Walshe, D. E., "Measurements of Wind Force on a Model of aPower Station Boiler House at Various Stages ofErection, " NPLAero Report 1165, National Physical Laboratory, AerodynamicsDivision, Teddington, UK, September, 1965.

ASCE, "Wind Forces on Structures", Transactions ofthe ASCEVol 126, Pages 1124-1198, 1962.

Nadeem, A, "Wind Loads on Open Frame Structures", M.S.Thesis, Louisiana State University, Baton Rouge, Louisiana, 1995.

NadeemlLevitan Nadeem, A, and Levitan, M.L., "A Refined Method forCalculating Wind Loads on Open Frame Structures",Proceedings, Ninth International Conference on Wind Engineering(January 9-13; New Delhi, India), 1995.

ASCE7 The 1995 edition of ASCE 7 and its predecessors. When noted byitself this reference is the 1995 version of this document. ASCE 7

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is titled "Minimum Design Loads for Buildings and otherStructures ". This document is the successor ofANSI A58.1.

American National Standards Institute ANSI A58.1 "MinimumDesign Loadsfor Buildings and Other Structures ", 1982.

C-2

INDEX

AAmerican National Standards Institute

(ANSI): ANSI A58.1, currentdesign practices 2-1, 2-2-2-3

American Society of Civil Engineers(ASCE): ASCE 7-88, currentdesign practices 2-1, 2-2-2-3;ASCE 7-95, differences in 3-1-32; ASCE 7-95, gUideline 4-1;ASCE 7, scope of 1-1-1-2

Appurtenances: base shear calculation5-20-5-21 ; calculation considerations 2-6; current vessel designs2-7-2-8; force coefficients example 5-11, 5-16; longitudinal windcalculations 5-28; solid areas 411-4-12; transverse wind calculations 5-26-5-27

Area of application of force (Ael 4-12

BBase shear: comparison on vessels 3

13-3-15, 3-17-3-18; horizontalvessels 5-26-5-29; transversewind calculations 5-27; verticalvessel example 5-20; vertical vessels 5-19-5-26

Bent space 4-2

CCable trays: comparison criteria 3

2-3-3; force coefficients 4-3; tributaryareas 4-3; wind forcemethod comparison 3-4-3-5. Seealso Pipe racks

Calculations: along wind force 510-5-14, 5-17; base shear, horizontal vessels 5-26-5-29; baseshear, vertical vessels 5-19-5-26;

I-I

crosswind force calculations 514-5-17; for secondary axis loadcombinations 4-22-4-24

Classification of structure categories,changes in 3-1

Codes and specifications, currentdesign practices 2-2-2-3, 2-5, 26-2-7

Components: base shear calculation5-20-5-21; calculation considerations 2-6; current vessel designs 27-2-8; force coefficients example5-11, 5-16; longitudinal wind calculations 5-28; solid areas 411-4-1 2; transverse wind calculations 5-26-5-27

Configurations: case studies 1 and 2comparisons 5-18; design windforce case study 4-14; frame plancalculation 4-28; horizontal vesselcomparison 3-16; load combinations example 4-29; open framestructure comparison 3-6-3-8;open structure framing plan 4-8;pipe load cases I-IV 3-3; piperock plan example 5-5; verticalvessel comparison 3-12; winddirections and secondary axis 425; wind load versus wind direction 4-25

DDecki ng 4-1 1Design guide, in surveys 2-1Design practices: horizontal vessel

wind force comparisons 3-17-318; open frame structure survey 25; open frame structure wind forcecomparisons 3-10-3-11; pipe

rack survey 2-2-2-3; pipe rack

wind force comparisons 3-1-3-5;pressure vessel survey 2-7-2-8;vertical vessel wind force compar

isons 3-1 3-3-15Design wind force: case study 4-13

4-16; equation, example 5-1;equation, explained 1-1; frame

load equation 4-5-4-6; main

force resisting systems equation 41; variances in practice 2-1. Seealso Winds

EEffective solid area (As) 4-1 2Equations: area of application of force

(Ae) 4-12; design wind force, F

(1 .1) 1-1, 4-1, 5-1; effective solid

area (As) 4-12; for frame loads,

Fs (4.1 a) 4-5-4-6; framing ratio,Cf (4.2) 4-7; main wind force

resisting system 4-4-4-5; shield

ing factor, (4.4) 4-15; solidity

ratio, (4.3) 4-11Equipment: considerations 4-14, 4

15; force coefficient example 511-5-12 5-16,

Exposure categories, velocity pressure

1-2, 5-1Exposure coefficients: changes in 3-1;

determining 5-1

FFlexible structures: gust effect factors

4-1, 5-2; load analysis of 5-25;recommendations on 2-4, 2-6;wind load comparisons 3-13-315. See also Pressure vessels

Floors, solid areas 4-11-4-12Force coefficients: along wind force

calculations 5-10-5-14, 5-17;

1-2

components and cladding 4-5-46; consideration 1:2; crosswind

force calculations 5-14-5-17;defined 4-2; for frame sets 4-74-11; frame sets and secondary

axis 4-21-4-22, 4-26-4-27;load combination example 4-29;maximum 4-7; open frame prac

tices 2-5; pipe rack practices 22-2-3; pipes and cable trays 43; pressure vessel practices 2·72-8

Frame loads: design wind force equations 4-5-4-6; force coefficients

for frame sets 4-7-4-11; framingratio 4-7;'solid area 4-11-4-12

Frame space ratio: calculation 5-105-11; crosswind force calculation

5- 15; equation 4·7

GGross (envelope) area 4-7, 5-10Gust effect factors: changes in ASCE

7-95 3-1-3-2; defined 4-1;determining 5-2; determining for

open frame structures 5-9; values

of 4-1Gust response fadors 1-2

HHorizontal vessels: design comparisons

3-17-3-18; design practices 27-2-8; determine force coeffi

cients 4-18-4-20; longitudinal

winds 5-27-5-29; transversewinds 5-26-5-27. See alsoPressure vessels

IImportance factors: changes in ASCE

7-95 3-1; consideration 1-2; cur·

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rent design practices 2-1; determining 5-1

Lload combinations: design load case

study 4-13, 4-14; secondary axiscalculations 4-22-4-24

lower bound: pipe load cases I-IV 34. See also Wind loads

MMain wind force resisting systems: con

siderations 4-4-4-5; example 511

Maximum probable loads 2-4, 3-4.See also Wind loads

Minimum probable loads 3-4. Seealso Wind loads

oOpen frame structures: along wind

force calculations 5-1 0-5-14, 517; alternate method 4-21-4-29;comparison criteria 3-5-3-9;components 4-5-4-6; crosswindforce calculations 5-14-5-17;current practice survey 2-5;defined B-1; design considerations

2-4; design load case studies 1and 2 4-13, 4-14; example criteria 5-1-5-2 5-9- frame sets 4-, ,7-4-11; main wind force resistingsystems 4-4-4-5; solidity equation 4-11-4-13; wind forcemethod comparisons 3-9-3-11

p

Pipe racks: comparison criteria 3-23-3; comparison of wind forcemethods 3-4-3-5; in current practices survey 2-2-2-3; defined B-

1-3

1; design considerations 2-1;example criteria 5-1-5-2, 5-3;guidelines for force coefficients 42; pipe and cable tray example5-3-5-5, 5-7; structure example5-4-5-7

Pipes: base shear calculation 5-215-22; force coefficients 4-3; solidity ratio and shielding example 513-5-14; tributary areas 4-2

Platforms: base shear calculation 522-5-25; longitudinal wind calculations 5-28

Pressure vessels: comparison criteria3-11-3-12, 3-15-3-16; considerations 2-6; defined B-1; designcomparisons 3-14-3-15, 3-173-18; design practices 2-7-2-8;determine force coefficients 416-4-20; and shear 3-13-3-15;vertical vessel example 5-19-525

Projected oreas, calculations for 4-2

RRigid structures: gust effect factors 5

2; wind loads 3-13-3-15. Seealso Pressure vessels

5Secondary axis: determining force

coefficients 4-21-4-22; loadcombination calculations 4-224-24

Shielding 1-2; along wind example5-13-5-14; current pipe rackpractices 2-2-2-3; factor equation 4-15; factors 2-4; andoblique wi nds 4-13; wind loadconsiderations 4-2

Solidity ratio: along wind force exam-

pie 5-10-5-11; crosswind force

colculation 5-15; explained 411-4-12

Specifications and codes: currentdesign practices 2-2-2-3, 2-62-7 5-2,

Spheres, force coefficients 4-19-420

Streamlining effect 4-12Structure classification categories,

changes in 3-1-3-2Structures: determining gust effect fac

tors 5-2; recommendtion on flexible 2-4, 2-6; rectangular 4-4;unclad framed 4-4; wind forceconsiderations 3-11

Supports: longitudinal wind calculations 5-28-5-29; transverse windcalculations 5-27

TTorsion 4-16Tributary areas 1-2, 4-2-4-3

UUpper bound: indirect shielding 2-4;

on pipe loads 3-4. See also Wind

loads

VVelocity pressure: determining 4-1;

example profile 5-2; exposurecoefficients 3-1; formula 5-1;open frame structures profile 5-9

Vertical aspect ratios 4-7Vertical vessels: base shear 5-20-5

25; design practices 2-7-2-8, 313-3-15; determine force coefficients 4-16-4-18; simplifiedmethod 5-19-5-20. See alsoPressure vessels

1-4

Volumetric solidity ratio: determining4-15; example 5-13-5-14

WWind loads: defined 4-13, 4-14;

research considerations 6-1--6-3.See also Equations; Design practices; Design wind force

Winds: along wind force calculations5-10-5-14, 5-17; angles of 4-7;crosswind force calculations 5-145-17; loads versus wind direction

4-25; longitudinal wind calculations 5-27-5-29; normal andquartering 4-21; oblique andshielding 4-1 3; transverse and

longitudinal 3-17-3-1 8; transverse wind calculations 5-26-527. See also Design wind force

Wind speeds 1-2Windward frame: solid area calcula

tion 5-10

Design of Anchor Bolts in

Petrochemical Facilities

Prepared by the

Task Committee on Anchor Bolt Design

ASCE Petrochemical Energy Committee

This publication is one of five state-of-the-practice engineering reports produced,to date, by the ASCE Petrochemical Energy Committee. These engineering reportsare intended to be a summary of current engineering knowledge and design practice,and present guidelines for the design of petrochemical facilities. They represent aconsensus opinion of task committee members active in their development. Thesefive ASCE engineering reports are:

1) Design ofAnchor Bolts in Petrochemical Facilities

2) Design ofBlast Resistant Buildings in Petrochemical Facilities

3) Design ofSecondary Containment in Petrochemical Facilities

4) Seismic Design and Evaluation ofPetrochemical Facilities

5) Wind Loads on Petrochemical Facilities

The ASCE Petrochemical Energy Committee was organized by A. K. Gupta in1991 and initially chaired by Curley Turner. Under their leadership, the five taskcommittees were formed. More recently, this committee has been chaired by JosephA. Bohinsky, followed by Frank J. Hsiu.

Frank J. HsiuChevron Research and Technology Co.

Chairman

Joseph A. BohinskyWilliam BoundsClay FlintJohn GeigelAjaya K. GuptaMagdy H. HannaSteven R. HemlerGayle S. JohnsonJames A. MapleDouglas J. NymanNorman RennallsCurley Turner

111

1. Marcell HuntHudson Engineering Corporation

Secretary

Brown & Root, Inc.Fluor Daniel, Inc.Bechtel, Inc.Exxon Chemical CompanyNorth Carolina State UniversityJacobs Engineering, Inc.Eastman Chemical CompanyEQE International, Inc.J.A. Maple & AssociatesDJ. Nyman & AssociatesBASF CorporationFluor Daniel, Inc.

ASCE Task Committee on Anchor Bolt Design

This report was prepared to provide guidance in the design of headed, cast-inplace anchor bolts for petrochemical facilities. Although the makeup of thecommittee and the writing of this document are directed at petrochemical facilitydesign, these guidelines are applicable to similar design situations in other industries.This report should interest structural engineers with responsibility for designingfoundations as well as operating company personnel responsible for establishinginternal design and construction practices. The task committee was established toprovide some uniformity in the criteria currently used in the petrochemical industry.

This report is intended to be a State-of-the-Practice set of guidelines. Theguidelines are based on published information and actual design practices. A reviewof current practice, internal company standards, and published documents wasconducted. The report includes a list of references to provide additional information.

In helping to create a consensus set of guidelines, a number of individualsprovided valuable assistance.

J. Marcell HuntHudson Engineering Corporation

Chairman

Van AiEd AlsamsamDon BoydHoward EdwardsJohn FalconJames LeePaul MorkenDale MuellerSam RameshAlan ShiveDan StoppenhagenHikmat Zerbe

IV

Randy RussJacobs Engineering Group, Inc.

Secretary

Jacobs Engineering Group, Inc.Sargent & Lundy EngineersParsons SIPParsons SIPJacobs Engineering Group, Inc.Brown & Root, Inc.John BrownLitwin Engineers & Constructors, Inc.Bechtel, Inc.Fluor Daniel, Inc.Fluor Daniel, Inc.Brown & Root, Inc.

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CONTENTS

Chapter 1: Introduction 1-1

1.1 Background 1-11.2 Objectives and Scope 1-11.3 Current State of Research 1-21.4 Future Codes and Procedures 1-2

Chapter 2: Materials 2-1

2.1 Introduction .2-12.2 Grades 2-12.3 Fabrication and Welding 2-12.4 Corrosion 2-1

Chapter 3: Design 3-1

3.1 Introduction 3-13.2 Petrochemical Anchorage Design 3-33.3 Bolt Configuration and Dimensions 3-33.4 Design Basis 3-43.5 Distribution of Anchor Bolt Forces 3-73.6 Checking Critical Modes of Failure 3-103.7 Pier DesignlReinforcing 3-16

Chapter 4: Installation .4-1

4.1 Introduction .4-14.2 Sleeves .4-14.3 Pretensioning .4-34.4 Considerations for Vibratory Loads .4-74.5 Considerations for Seismic Loads (Zones 3 & 4) .4-7

Nomenclature A-lReferences B-1

v

1

CHAPTERlINTRODUCTION

1.1 BACKGROUND

Due to limited coverage of anchorages in the commonly used design codes, mostpetrochemical engineering firms and owner companies use an extrapolation,variation, or interpretation ofACI 349, Appendix B, "Code Requirements for NuclearSafety Related Concrete Structures, " to design anchorages. Also, ACI PublicationAB-81, "Guide to the Design of Anchor Bolts and Other Steel Embedments," isfrequently used as the basis for the design of anchorage systems for thepetrochemical industry. The lack of a single, authoritative design standard hasresulted in inconsistent design and details. This committee's work has beeninfluenced by the need to develop a uniform anchor bolt design methodology that isacceptable throughout the petrochemical industry.

1.2 OBJECTIVES AND SCOPE

The objective of this committee report is to:

a. Evaluate current petrochemical industry anchor bolt design methods.

b. Gather information regarding proposed changes and new releases of designcodes which contain procedures for anchor bolt design.

c. Provide the engineer with information and recommendations that supplementcurrent codes for design of headed, cast-in-place anchor bolts.

The committee recognizes that several different types of anchorage systems areused in petrochemical facilities, but the most common type is a cast-in-place, headedbolt. Therefore, for this report, the committee limited its investigation andrecommendations to the cast-in-place, headed bolt. This self-imposed limit shouldnot be construed as an attempt to limit the importance of other types of anchoragesystems, but it provided a means of focusing the committee's attention on the mostcommonly used device.

1-1

1.3 CURRENT STATE OF RESEARCH

Test results are limited for bolts that are in the upper range of sizes andembedment depths that are commonly used in petrochemical facilities. A majorityof embedment depths that have been tested are less than 7.87 inches (200 mm ) withvery few, if any, greater than 21.65 inches (550 mm). Most bolt sizes that have beentested are less than 2 inches (50 mm) in diameter, and a majority of the tests havebeen performed on bolts that are I inch (25 mm) or less in diameter.

Very little testing has been done that accounts for the effect of reinforcing onanchor bolt capacity in shear, tension, or both. Limited testing has been done whichattempts to identify edge distance or anchor spacing influences. Lee and Breen(1966) reported on results for 26 bolts and Hasselwander, Jirsa, Breen, and Lo(1977) published a report based on results for 35 bolts. Baily and Burdette alsopublished a report in 1977 entitled "Edge Effects on Anchorage to Concrete. "

Recently, Fuchs et a!., published a code background paper, "Concrete CapacityDesign (CCD) Approach/or Fastening to Concrete", which presented an approachdifferent from the well-known provisions of ACI 349. Furche et aI, performedpullout tests with headed studs placed near a free edge and recommended anempirical equation for calculating the failure load in their paper titled "Lateral Blowout Failure a/Headed Studs Near a Free Edge".

1.4 FUTURE CODES AND DESIGN PROCEDURES

ACI Committee 318 is currently working to add a chapter on anchorages to afuture issue or a supplement to AC1318.

In 1991, ACI Committee 355 published, a "State-of-the-Art Report onAnchorage to Concrete." This is the first of a two-volume set which emphasizesbehavior and does not include design methods and procedures. They are currentlyworking on the second volume, which will be a design manual, for anchorageswhose capacity is computed based on unreinforced failure cones.

The ACI 349, Appendix B, subcommittee is reviewing additional anchor bolttesting to cover situations not covered by present test results (bolts close to the edgesof concrete, closely spaced bolts, etc.). They plan on rewriting ACi 349, AppendixB, after they review the results of these tests. The planned rewrite will be basedupon the Concrete Capacity Design (CCD) method (See Section 3.1 of this report.)with modifications to account for the results from this additional testing.

Information from these various ACI committees indicates that changes will bemade to some of the formulas and methodologies that are currently being used. Thetrend appears to be moving from the ACI 349 method toward the CCD Method.

1-2

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CHAPTER 2MATERIALS

2.1 INTRODUCTION

This chapter provides basic materials and corrosion protection recommendationsfor anchor bolts. Selection of the proper grade, strength, weldability, and corrosionresistance must be considered so that the anchor bolt will perform as the engineerintends.

2.2 GRADES

Table 2.1 lists the ASTM specifications, yield strength, ultimate strength, andrange of available diameters for materials commonly used for anchor bolts.

2.3 FABRICATION AND WELDING

Flux, slag, and weld-splatter deposits should be removed before galvanizingbecause the normal pickling process does not remove slag. Toe cracking atweldments around anchor plates is undetectable prior to galvanizing and is easilydetected after galvanizing. A post-galvanizing inspection should be considered todetect these cracks.

Materials which have been quenched and tempered should not be welded or hotdip galvanized. High-strength materials should not be bent or welded since theirstrength and performance may be affected by bending or heating.

2.4 CORROSION

Anchor bolt service life requires that corrosion protection be an importantdesign consideration. Anchor bolt material or coating system selection shouldprovide a reliable and high-quality service life for an item that is relatively

2-1

Table 2.1: Common Materials for Anchor Bolts

ASTM Fy' Fut' Diameter Range,Specification ksi (MPa) ksi (MPa) inches (mm) Notes

Bolts AI93 Gr B6 85 (590) 110 (760) to 4 (l02) NGand AI93 GrB7 105 (720) 125 (860) to 2 1/2 (64)Studs 95 (660) lIS (790) over 2 1/2 (64) to 4

75 (SIS) 125 (860)(102)over 4 (l02) to 7 (l80) NG

A307 60 (410) to 4 (102) WCEA325 92 (630) 120 (830) 1/2 (13) to I (25)

81 (560) 105 (720) over I (25) to I 1/2 (38) 1mA354 Gr 8e 109 (750) 125 (860) "1/4 (6) to 2 1/2 (64)

99 (680) lIS (790) over 2 1/2 (64) to 4(l02)

A354 Gr BD 130 (900) 150 (1030) 1/4 (6) to 2 1/2 (64) SC,115 (790) 140 (970) over 2 1/2 (64) to 4 NG

(l02)A449 92 (630) 120 (830) 1/4 (6) to I (25)

81 (560) 105 (720) over I (25) to 1 1/2(38)

58 (400) 90 (620) over I 1/2 (38) to 3 (76)A490 130 (900) 150 (1030) 1/2 (l3) to I 1/2 (38) ImNGA687 105 (720) ISO (l030) 5/8 (l6) to 3 (76)

Threaded A36 36 (250) 58 (400) to 8 (200) WRound A572 Gr42 42 (290) 60(410) to 6 (l50)Stock A572 Gr 50 50 (340) 65 (450) t02(5])

A588 50 (340) 70 (480) to 4 (102)46 (320) 67 (460) over 4 (102) to 5 (127)42 (290) 63 (430) over 5 (127) to 8 (200)

B21 Temper H02 27 (190) 60 (410) 1/2 (13) to 1 (25) 8rAlloy UNS C46400 26 (180) 58 (400) over 1 (25) to (51)Alloy UNS C48200 25 (170) 54 (370) over 2 (51) to 3 (76)

22 (ISO) 54 (370) over 3 (76)B98 Temper H02, 20 (140) 55 (380) 1/2 (13) to 2 (51) BrAllov UNS C651 00898 Temper H02, 38 (260) 70 (480) t02(51) BrAllov UNS C65500F1554 Gr 36 36 (250) 58 (400) 1/4 (6) to 4 (l02) WF1554 Gr 55 55 (380) 75 (520) 1/4 (6) to 4 (102\ WSIF1554Gr 105 lOS (720) 125 (860) 1/4 (6) to 3 (76\

Notes: WCE1mSCNGWBrWSI

Weldable if carbon equivalent:s 0.35%.Impractical because of limited available length.Susceptible to stress-corrosion cracking.Galvanizing is not an option in the ASTM specification.Weldable.Brass alloy.Weldable with Specification's Supplementary Requirements S I.

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inaccessible for maintenance, repairs, or replacement due to corrosion. There aremany factors and environmental exposure conditions that should be considered. Theengineer may need to consult with materials specialists about corrosion protectionduring the anchor bolt material selection process.

2.4.1 Environmental Conditions

Anchor bolts near waterways and seashores require corrosion protection againstwet-dry cycles and excessive salts. De-icing salts in runoff from areas with snowand ice can also be particularly corrosive to anchor bolts.

Anchor bolts located in controlled environments inside buildings should notrequire protection from atmospheric corrosion except for exposure to chemicals.

Anchor bolts encased in concrete should not require corrosion protection unless.sulfates or chlorides are present in the concrete. Joints in concrete should be sealedto keep moisture from anchor bolts.

Galvanized and stainless materials can fail when subjected to corrosivechemicals such as acids or other industrial fumes. Such materials require additionalcoating systems.

Bare, uncoated, weathering steels should not be used where high concentrationsof corrosive chemical or industrial fumes are present.

2.4.2 Codes and Specifications

2.4.2.1 American Concrete Institute (ACI)

ACI 318-89 requires that protection be provided from injurious amounts of oil,acids, alkalis, salts, organic materials, or other substances that may be deleterious tothe concrete, the reinforcing, and the anchor bolts.

ASTM A 767 and A 775 specifY a zinc coating and an epoxy coating of steel barsfor concrete reinforcing in highly corrosive environments.

The soluble chloride ion content in concrete is controlled by ACI 318-89,Section 4.3.1; also see the report by ACI Committee 222, "Corrosion ofMetals inConcrete. "

When external sources of chlorides are present, increased concrete cover and/oran epoxy coating should be provided for reinforcing bars, in accordance with ACI318-89, Sections 4.3.2 and 7.7.5. Anchor bolts should be considered as an extensionof the concrete, as noted in ACI 318-89, Section 7.7.6, which requires that exposed

2-3

reinforcement, inserts and plates intended for bonding with future extensions beprotected from corrosion.

2.4.2.2 American Institute of Steel Construction (AISC)

Anchor bolt corrosion and material selection is outside the scope of AISCspecifications or codes. The "Steel Design Guide Series, Volume 7", includes achapter to assist in some of the practical aspects of design and application of anchorbolts.

The "Steel Design Guide Series, Volume 1" recommends that anchor boltssubjected to corrosive conditions be galvanized. If anchor bolts are galvanized, it isbest to specify ASTM A307 and A36 material to avoid embrittlement that sometimesresults when high-strength steels are galvanized.

Weathering steels may be used when anchor bolts are exposed to corrosiveatmospheres, but it should be understood that they will rust and stain the foundationconcrete if so exposed.

2.4.2.3 American Petroleum Institute (API)

API 650 states that when corrosion is a possibility, an additional thicknessshould be considered for anchors. It is recommended that their nominal diameter notbe less than I inch (25 mm) and that a corrosion allowance of at least 1/4 inch (6mm) on the diameter be provided.

API 620 recommends using stainless steel anchorage materials or providing acorrosion allowance when using carbon steels.

2.4.3 Corrosion Rates

There are substantial variations in corrosion rates even under relatively similarconditions. Corrosion rates that are cited or determined by technical sources canvary in actual service life. During the design of anchor bolt protection systems,materials and process engineers should be consulted to define the corrosive exposureelements and what material or coating system is best suited for protection.

2.4.4 Coatings

If anchor bolts are in an area where the environment is particularly corrosive orabrasive, special coatings are required. Protective coatings may be preferable toincreasing the bolt diameter or the length of embedment for the anchor boltassembly. Polyamide epoxies and urethanes for carbon steel anchor bolts provideprotection against alternating wet-dry environments. Phenolic epoxy coatings

2-4

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provide protection for chemical and acid vapors or fumes which exist m someindustrial atmospheres or environments.

2.4.4.1 Considerations for Coating

A corrosion allowance is not required for anchor bolts that are galvanized orcoated. Anchor bolts that are not galvanized or coated should have a minimumcorrosion allowance of 118 inch (3 mm) added to their diameter.

All types of protective coatings should be periodically inspected and maintainedto prevented corrosion from reducing the design capacity of the anchor boltassembly.

Anchor bolts should be kept free of accumulations of excess materials or debristhat may contain or trap moisture around anchors. Concrete surfaces should besloped to drain water. Avoid details which will create pockets, crevices, and fayingsurfaces that can collect and accumulate water, debris, and other damp materialsaround the anchor bolt.

Foundations located in areas with a high ground-water table are highlysusceptible to corrosion. The diameter of anchor bolts exposed to surface drainageor ground water should be increased a minimum of 118 inch (3 mm) for corrosionprotection unless a protective coating is provided.

The surfaces between base plates and the concrete and/or grout pads should besealed to prevent the infiltration of corrosive elements. Cement-sand, dry-pack groutpads should be coated or sealed in areas with cyclic wet-dry environments.

The service life of a combined system of paint over galvanizing is substantiallygreater than the sum of lives of the individual coatings. Precautions must be taken toensure adherence of the paint to the galvanized surface, which is smooth and doesnot permit mechanical locking of the coating film.

2.4.4.2 ASTM A153, Hot Dip Zinc

Galvanizing with a hot-dip zinc process provides a cost-effective andmaintenance-free corrosion protection system for most general applications.Precautions against embrittlement should be taken by the designer, the fabricator,and the galvanizer in accordance with recommended practice in ASTM AJ43. Acoating weight of I to 2.5 ounces/square foot (0.3-0.75 kg/m2) is normal for the hotdip process. A recommended thickness of 2.3 ounces/square foot (0.7 kg/m2) is anaverage application requirement. A corrosion allowance should not be required oradded to galvanized anchor bolts.

2-5

Steel material with a tensile strength less than approximately 125 ksi (860 MPa)can be hot-dip galvanized, if that is an option in the appropriate ASTM specification(See Table 2.1). Steel material with a greater strength should not be hot-dipgalvanized. As the yield stress increases, the possibility of hydrogen embrittlementincreases because hydrogen is absorbed into the steel during the pickling process.Blast cleaning rather than pickling should be used for alloy materials.

Electro-deposited zinc coating can be applied to 1 inch (25 mm) diameters andsmaller. Material sizes larger than a 1 inch (25 mm) diameter can be coated with aninorganic zinc-rich paint or other coating system specifically selected for corrosionprotection.

A wet storage stain (white rust) should be prevented. Wet stain is a"voluminous white or gray deposit." It can form when closely packed, newlygalvanized items are stored or shipped in damp or poorly ventilated conditions. Thisshould not be confused with the normal process of weathering of the galvanizedcoating.

2.4.4.3 Cold-Applied Zinc

A cold-applied, organic, zinc-rich compound primer or coating should be usedfor field touch-up of galvanized bolts that have areas damaged during shipment orerection. Commercial zinc products for touch-up are zinc-rich paint, zinc spraying,or brushed molten zinc. A touch up paint should have 94% zinc dust in the dry filmand should be applied to a dry film thickness of 8 mils (0.20 mm), minimum. Referto ASTMA 780 for additional information.

2.4.4.4 Insulation and Fireproofing

Anchor bolts encased in weathertight or cementious insulation or fireproofingrequired for equipment normally do not require corrosion protection. If conditionsexist for moisture to collect under the insulation or fireproofing, the anchor boltsshould be coated with a zinc-based primer or other coating similar to that to be usedfor the equipment. Two coats of primer, for a total dry film thickness of 3-4 mils(0.08 to 0.10 mm), should provide the necessary corrosion protection for this service.

2.4.5 Weathering Steel (ASTM A588)

Weathering steels develop a tight oxide coating that protects against corrosion ofthe substrate. In certain environments, they will provide a relatively maintenancefree application. The material will form a protective surface with loss of metalthickness of about 2 mils (0.05 mm). Steels conforming to ASTM A588 will provideatmospheric corrosion resistance that is 4 to 6 times the corrosion resistance ofordinary carbon steels.

2-6

50 MPa)ificationhot-dip

ttlementprocess.

ters andwith an

:JrrOSIOn

,m IS a, newlyIS. Thisvanized

be usedment orJraymg,iry film. Refer

roofingIditionsJr boltsbe used-4 milsservIce.

'sion of:nancef metalJrovidemce of

Bare weathering steel should not be submerged in water because this steel willnot provide corrosion resistance greater than a black carbon steel in the same service.Bare weathering steel should not be exposed to recurrent wetting by salt water,spray, or fogs because the salt residue will cause accelerated corrosion.

Weathering steels may be painted or galvanized as readily as carbon steels,although their appearance may not be uniform as a result of the higher siliconcontent. If urethane foam or other fire-retardants are to be used to protectweathering steels, consideration should be given to the fact that they can be verycorrosive when wet with water. If paint is a consideration, consult the foam supplierfor a recommendation of the paint system that is compatible with their foam.

2-7

CHAPTER 3DESIGN

3.1 INTRODUCTION

In the past, there has been a decided lack of guidance in building codes for thedesign of anchorages to concrete. As a result, engineers have used experience,knowledge of concrete behavior, and guidance from other design recommendations(such as ACI 349, Appendix B) for help in designing these anchorages. In the future,however, this will likely change as ACI 318 is working to introduce a new section ofcode addressing this important area ofdesign. The proposed new code language willalso recommend a design method that is somewhat different from that currently usedby most engineers in the petrochemical industry. This method, as described in thepaper by Fuchs et al., is currently considered the state-of-the-art in anchor boltdesign in non reinforced concrete. However, it is not the current state of practice inthe petrochemical industry, where due to the small concrete sections, thereinforcement is used for transfer of anchor bolt forces to concrete.

The method, called the Concrete Capacity Design (CCD) method, is similar inprinciple to the method used by ACI 349, Appendix B, but has the followingdifferences:

a. The ACI 349, Appendix B, method uses a conical failure surface for bothtensile and shear loading. The CCD method uses a pyramid.

b. The ACI 349, Appendix B, method uses a failure slope of 45°, as opposed tothe 35° failure slope used by the CCD method.

c. The ACI 349, Appendix B, method uses formulas for tension and shear whichare proportional to the square of the depth of embedment and edge distance,respectively. Instead of using an exponent of 2 in these equations, the CCDmethod uses an exponent of 1.5.

Other than the change from the cone to the pyramid model, which was invokedto simplify the computations, these changes are based on empirical evidence drawn

3-1

)r theence,Itionsuture,on ofewillusedn the- bolttcem, the

ed to

IhichInce,CCO

okedrawn

from experimentation m the United States and Europe and on theoreticalconsideration of variables such as size effect. For more information on the basis forthe proposed changes, the user is referred to the paper by Fuchs, et al. This paperdetails how testing has revealed that the CCO method is a more accurate predictor ofconcrete capacity for various anchorages, which has also been verified byprobabilistic studies by Klingner, et al. Furthermore, the experimental evidencepresented in the paper by Fuchs et aI., shows that, for certain conditions, the modelsused in ACI 349, Appendix B, can actually overpredict the anchorage capacity (whenusing a t/J, strength reduction factor, of I). Therefore, the anchor bolts at the deeperembedments found in petrochemical design can be undersized using this method.The reader should be cautioned, however,that the amount of testing done on anchorbolt arrangements, bolt sizes, and depths of embedments typically found in thepetrochemical industry is extremely limited, and is constrained to bolt sizes andembedments found close to the minimum sizes used in the petrochemical industry.Therefore, it is difficult to draw definite conclusions about the accuracy of usingeither method for larger bolts and deeper embedments without furtherexperimentation.

The effects of the changes on design, however, can be easily demonstrated bylooking at the formulas. Based on the changes described above:

a. For tension, the ACI 349, AppendiX B, method will give smaller capacity forshallow embedments and greater capacity at deeper embedments than theCCO method. This is attributed to the exponent difference (2 for the ACImethod; 1.5 for the CCO method).

For both shear and tension and anchor bolts close to an edge or close to otherbolts, the ACI 349, AppendiX B, method allows smaller edge distances andbolt spacing before the capacity of the anchorage is reduced. This resultsfrom the change in angle of the failure surface. (45 0 ACI, 350 CCO)

For bolts close to an edge and subjected to shear, the ACI 349, Appendix B,method will give lower anchor capacities at close edge distances and largeranchor capacities at large edge distances than the CCO method, because ofto the exponent difference on the edge distance.

d. For anchors close to a comer, the capacity of a bolt according to the ACI 349,Appendix B, method is higher because of severe reductions by the CCOmethod for biaxial load effects.

All of these factors point to the fact that design by the CCO method willgenerally produce more conservative designs for the bolt sizes and embedmentstypically found in petrochemical design. However, the paper by Fuchs, et al. alsonotes that the method was primarily developed for anchors in unreinforced concreteand that the use of reinforcement designed to engage failure cones/pyramids could

3-2

substantially increase the load capacity of the anchorage. Early evaluation of theCCD method for typical examples in petrochemical design supports the observationof more conservative results and found that, without the use of reinforcing, thismethod would lead to unacceptably conservative concrete member sizes.

This report is intended to give guidance for design of anchorages found in thepetrochemical industry. Therefore, based on the observations above, it will identifythe critical steps in anchor bolt design and will make recommendations for providingreinforcing detai Is to provide safe and economical reinforced concrete designs.

3.2 PETROCHEMICAL ANCHORAGE DESIGN

Design of foundations in petrochemical design often involves the anchorage oftall vessels and structures subjected to heavy wind and seismic forces, resulting inlarge diameter anchor bolts. To transfer the loads from the anchor bolts to thereinforced concrete foundation, the embedment length of these anchor bolts cansometimes become quite large, and it is not uncommon for these anchor bolts tocontrol the depth of the foundation.

The size of the concrete members in which the anchorage is embedded is oftenlimited by the available space, which is often severely restricted by piping andelectrical conduit, as well as by other foundations and access requirements. Becauseof the size and configurations of anchorages used in the petrochemical industry,design decisions often involve different choices not found in other industries. Theflow chart shown in Figure 3.2 shows the design path that an engineer typicallyfollows when designing an anchorage to concrete using a headed bolt.

3.3 BOLT CONFIGURATION AND DIMENSIONS

3.3.1 Bolt Configuration

The bolt configuration consists of either a headed bolt or a steel rod with threadson each end. ASTM A36 rods have one nut tack welded to rod at the end which isembedded in concrete. For high strength material which is not weldable (such asASTM A193), two nuts are provided at the end embedded in concrete. The two nutsare jammed together before bolt installation to prevent loosening when the top nut istightened.

AC1349-90, Section B4.5.2 does not differentiate between ASTM A36, A307 andhigh strength bolts. For high strength bolt assemblies such as ASTM A193, due tothe very high bearing stress at the nut, it is recommended that a standard washer, ofmaterial compatible with the threaded rod material, be used. See Section 3.6.4 forwasher requirements at high strength bolts.

3-3

(

rt

3

adtltl

f theation. this

n thentifyiding

'e of,19 III

) thecan

ts to

)fienand

ausestry,The

;ally

/ HIGH-STRENGTH BOLT WIHEAVY HEX NUT

TOP OF CONCRETE

.. ... . ~. .... ' " .... ..TIGHTEN NUTS TO LOCKAPPLY TORQUE TO BOTTOM NUT

;ASTMA36

SJACKWRD

\LOCK BOTH NUTS BY COUNTER PUNCHING THETHREADS AT JUNCTURE OF NUT & BOLT

Figure 3.1: Anchor Bolt Head Configurations

3.3.2 Dimensions

The following minimum bolt dimensions are assumed in this section. Thedimensions are insufficient for developing bolt loads in concrete and therefore pierreinforcement is required for load transfer. The dimensions are in conformance withthe typical dimensions used in the petrochemical industry.

eads;h ish asnutsut is

Embedment:Minimum Edge Distance:

Minimum Bolt Spacing:

3.4 DESIGN BASIS

Minimum embedment should be 12 bolt diameters4 x bolt diameter for ASTM A307 or A36 bolts6 x bolt diameter for high strength bolts8 x bolt diameters

and'e tor, of. for

Depending upon the loads used for anchorage design and details of theanchorage, anchor bolt connections are classified as ductile or nonductile. Forductile connections, the embedment is proportioned using the ultimate capacity ofthe actual bolt. For nonductile connections, the embedment is proportioned usingthe factored design load.

3-4

A ductile connection can be defined as one that is controlled by yielding of steelelements (anchor bolt or reinforcement) with large deflections, redistribution ofloads, and absorption of energy prior to any sudden loss of capacity of the anchorageresulting from a brittle failure of the concrete. ACI 318 and other building codesfavor ductile design.

As a minimum, anchorage design loads should be factored service loads, asrequired by ACI 318. However, there are valid reasons why the engineer maychoose the design load to be the ultimate tensile capacity of the bolt. Reasons formaking the anchor bolt, rather than the reinforcement, the "weak link" include easierdetection and repair of damage from overload.

Sometimes client specifications dictate that design based on the ultimate capacityof bolts should be selected, but often the engineer must choose whether or not to usethe ultimate tensile capacity of the bolt to determine the required embedment. Thisdecision is an important one since it often affects the cost of the connections. Thecost of connections using factored loads is generally less than those using ductiledesign as the design basis. Because of conservative bolt sizing by equipmentmanufacturers, corrosion allowances, and inherent conservatisms that result from theprocess of sizing a bolt by allowable stress and the concrete anchorage by ultimatestrength, it is not uncommon for design based on the ultimate capacity of bolt toproduce design forces on bolts which are more than twice the factored service loads.

The engineer should base the decision of design basis on client specifications,building code requirements, the nature of the applied loads, the consequence offailure, and the ability of the overall structural system to take advantage of theductility of the anchorage.

3.4.1 Nature of Applied Loads

When peak loads are applied in a short-term or impulsive fashion, connectionsbased on the ultimate tensile capacity of the bolt can enable a structural support tocontinue to carry loads until the short-term peak has passed.

Likewise, anchorage design should allow for the redistribution of loads andabsorption of energy, as required in seismic or blast-resistant design. When thecharacteristics and magnitude of the load are unusually unpredictable, the anchoragedesign should be based on the ultimate tensile capacity of the bolt.

3-5

,f steelion of10ragecodes

Detennine distributionof forces

_--c'JL -~~Determine Anchor

Boll Loads

ids, asr mayms foreasier

.~~-_.Select Anchor

Bolt

JSize Concrete

Section

,,

~_._-'---I Design Concrete

Section forAnchor Bolt Loads I

L__~ _

IsConcrete Capacity

~ Greater than Steel~ Capacity?

"-·N<>

IYes

1 ...1---__-->1

Design Reinforcingfor

Anchor Bolt Loads

IsAnchorage Required "-....___ ~__

lobe > Yes

Ductile?

c------i

I DesignL--------cl~~ I Complete

LNO~

~. J-Design ConcreteSection for

Anchor Bo~_~oads

Itions,lce ofof the

.pacityto use

This. Theluctilepment1m thetimatelolt to.oads.

Figure 3.2: Headed Anchor Bolt Design Flowchartctions10rt to

3.4.2 Consequence of Failure

is and:n thelorage

In some cases, the consequence of the failure of a single anchorage may beparticularly undesirable. If, for instance, the failure of a single anchorage would leadto the collapse of a vessel or piping which contains highly flammable, toxic, orexplosive materials (particularly polyfloric materials which explode when exposedto air), the engineer may want to base the anchorage design on the ultimate tensilecapacity of the bolt. However, this decision depends on the characteristics of thestructure, as described in the next section.

3-6

3.4.3 Ability of Overall Structural System to Take Advantage of Ductility

If yielding of a ductile connection produces a hinge in a structure which leads toor causes a brittle failure elsewhere in the structure, the benefits of this ductility are,at best, underutilized.

3.4.4 Conclusion

It is the opinion of this committee that transfer of anchor bolt load toreinforcement in the supporting member will produce a ductile design, provided thereinforcement is properly detailed to yield prior to concrete failure.Recommendations for detailing reinforcing steel are listed in Section 3.7 of thisreport.

Anchorage design should be approached as a global structural design issue,focusing more on the development of ductile load-resisting paths as opposed to theductility of a single element. Once these load paths are developed, the engineer canthen correctly assess the effect of a ductile connection and decide the requirementsthat should be imposed on an individual anchor.

3.5 DISTRIBUTION OF ANCHOR BOLT FORCES

Before an anchor bolt can be designed, the maximum force in the bolt must bedetermined. As stated above, this design basis should depend on the nature of theapplied load.

An anchorage is ductile if the capacity of the concrete for each of the modes offailure is greater than the yield capacity of the bolt or reinforcement. If the bolt is tobe the ductile element, then the design of the reinforced concrete elements dependsonly on the size of the bolt. The size of the bolt, however, can only be determinedwhen the forces applied to the anchor group are distributed to the individual anchorelements (unless the bolt is sized by the equipment manufacturer).

If the anchorage is to be nonductile, the forces that are used to design theconcrete elements are the forces that result when the factored loads are distributed tothe anchor group. Sizing of the bolt requires that the distribution of forces underservice loads be determined. Therefore, in both ductile and nonductile design, theforces applied must be distributed to the anchor elements. The assumptionsregarding this distribution, however, can vary depending on the type of designchosen.

3-7

1

II

3

a

3.5.1 Distribution of Tension in Anchorages

Petrochemical structures supported by anchorages may be divided into twogeneral categories. One is typified by a vertical vessel with anchor bolts around itsperiphery, and the other is typified by a structural column with anchor bolts clusterednear the column.

3.5.1.1 Vessel Anchor Bolts

For a vertical vessel, anchor bolt maximum tension is commonly calculated byassuming an elastic distribution of forces and moments, which is based on themoment of inertia of the bolt group.

. 4MTensIOn = --

NxBC

where:

W

N(3.1)

M = maximum moment on vessel, kip-in (N-mm)N = number ofanchor boltsBC = bolt circle diameter, in (mm)W minimum weight of vessel, kip (N)

Use of Equation 3.1 conservatively assumes that the moments are resisted onlyby the bolt group, and does not take into account the contributions of the base platein resisting the moment, and does not consider strain compatibility between theconcrete and steel elements which comprise the anchorage. Although a straincompatibility procedure is described in Blodgett, it is very complicated to performby hand for most vessels with a ring baseplate and a circular anchor boltarrangement. Properly including effects of flexibility of the vessel and its supportingskirt would further complicate analysis.

With a simplifYing assumption of plane sections remaining plane and through theuse of computers, however, it is possible to iterate to a solution which solves for thelocation of the neutral axis and determines the compressive forces under thebaseplate ring and the tensile forces in the bolt. As stated previously, the design ofanchorages for tall vessels and stacks can often control the design of the foundation.This procedure may, therefore, be worth undertaking when the above equation yieldslarge anchor bolt sizes and embedments.

3.5.1.2 Structural Column Anchor Bolts

For a strength design, the design assumptions and general principles andrequirements of the ACI 3J8, Chapter 10, should be used to determine capacity of ananchorage at a structural column. Anchor bolts should be sized as if they werereinforcement in a conventional concrete short beam-column.

3-8

For a structural column, anchor bolt tensions should be determined by a methodwhich considers strain compatibility and equilibrium of forces and moments. Onesuch method, based on reinforced concrete working stress design procedures, hasbeen published by Blodgett.

Analysis of the anchorage as a reinforced concrete section should conform to thefollowing guidelines, in addition to the requirements ofA CI 318:

a. Anchor bolts should be considered as reinforcement, with area equal toanchor bolt tensile stress area. Tensile stress area is tabulated in the AISCASD Manual and AISC LRFD Manual for bolt diameters up to 6 inches (150mm).

b. If there is shear on the anchorage, it may be carried by anchor bolts in thecompressive region of the section. If these bolts do not provide sufficientshear resistance, then analysis of the section should use a reduced anchor boltarea to account for reduced bolt tensile capacity. One expression for reducedanchor bolt area is

(3.2)

where:

A'ff = effective anchor bolt area for resisting tension, in2 (mm2)

A, = anchor bolt tensile stress area, in2 (mm2)

Vu = ultimate shear per bolt, kip (kN)I/J = strength reduction factor = 0.85Ii = friction coefficient from A CI 349, Appendix B

= 0.55 ....when the bottom of the base plate is raised above theconcrete surface, as on a grout bed

= 0.70 ....when the bottom of the base plate is on the concretesurface

= 0.90 ....when the top of the base plate is at or below the concretesurface

f y = anchor bolt yield stress, ksi (kPa)

c. The concrete cross-section should be the concrete area beneath the base plate.

For the analysis to be valid, two additional constraints must be present. First, theanchorage must develop the yield strength of the anchor bolt. Second, the base platemust be sufficiently thick (or stiffened) so that it does not form a mechanism withplastic hinges before the anchor bolts yield. One way to ensure adequate base plate

3-9

j

j

s1

toC;0

lentlit~d

2)

he

:te

:te

teo

helteithlte

thickness is to provide a thickness so that prying force, when calculated In

accordance with the AISC ASD Manual and AISC LRFD Manual is insignificant.

3.5.2 Distribution of Anchor Bolt Shears

3.5.2.1 Means of Carrying Shear

In general, shear applied to an anchorage may be carried by one of the followingmechanisms:

a. Friction due to net compression and to compression due to moment couple.(This is a nonductile mechanism.)

b. Anchor bolts.

c. Embedments such as shear keys. It is essential that grout completely fill ashear key slot, and use of grout holes in the base plate is suggested. Whenshear keys are used, they should be sized to carry the entire anchorage shear,because shear keys are stiffer than anchor bolts in shear.

3.5.2.2 Shear in Ductile Anchorage Groups

If shear capacity of anchor bolts not carrying tension exceeds total design shear,then anchor bolts carrying tension may be assumed to carry no shear.

If total design shear exceeds shear capacity of anchor bolts not carrying tension,then anchor bolts carrying tension should be assumed to carry the difference. Shearamong tensile anchor bolts may be apportioned to minimize overall boltrequirements. This assumption is valid, since the plastic deformation capabilities ofa ductile anchor allow the loads to redistribute in the most efficient way.

3.5.2.3 Shear in Nonductile Anchorage Groups

If friction capacity exceeds applied total design shear, then anchor bolts may beassumed to carry no shear.

If total design shear exceeds friction capacity, then all shear should be assumedto be carried by the anchor bolts. Each bolt should be assumed to carry shear inproportion to its cross-sectional area, neglecting bolts having shear capacity limitedby edge distance.

3.6 CHECKING CRITICAL MODES OF FAILURE

Once the design force in the anchor bolt has been determined, the concrete andsteel elements which comprise the anchorage must be designed to resist these forces.

3-10

The forces applied to the individual anchor must be safely transferred to thesupporting member. This process involves checking the steel bolt for failure, as wellas checking the various critical modes of failure for the concrete. For a bolt intension, these modes of failure include:

* Bolt tensile failure* Pullout (concrete tensile) failure* Lateral bursting (blowout) failure* Localized bearing failure* Concrete splitting failure

At present, the anchor bolt design practice of the petrochemical industry is tosize concrete elements by strength design methods and to size steel elements mostlyby allowable stress design (ASD) methods.

3.6.1 Bolt Failure

Historically, the most common anchor bolt materials used in the petrochemicalindustry have been ASTM A307 or A36 for low-to-moderate strength requirementsand ASTM A193 Gr B7 for high-strength requirements. For these grades of bolts,many engineers have commonly used allowable stresses lower than those pennittedby AISC. In many cases, these lower allowable stresses have been justified by thedesign engineer to account for uncertainty in analysis, to pennit future additions tostructures, to reflect the critical role that the anchor bolts play in the structuralintegrity of the structure, and to reflect the relatively low cost of anchor bolts whencompared to the cost of failure. In other cases, engineers have simply been obligatedto comply with owners' specifications which have specified lower allowable loadsfor the same basic reasons. The following table compares allowable loads specifiedby an owner, using tensile stress area, with those pennitted by AISC ASD for a 2inch (51 mm) diameter bolt.

Table 3.1: Comparison of allowable bolt loads for 2 inch diameter A36 andA193 Grade B7 bolts

Owner AISCASD Owner AISCASDBolt Material allowable tensile allowable shear capacity

tension capacity shear kips (kN)kips (kN) kips (kN) kips (kN)

A36 48 (10.7) 60 (13.3) 25 (5.5) 41 (9.1)AI93 Gr B7 100 (22.2) 130 (28.9) 26 (5.8) 86 (19.1)

3-11

theNellt in

3.6.1.1 Combined Tension and Shear

a. Ultimate Strength Design

For bolts subject to both tension and shear, the following conditions shouldbe met:

(3.3)

s to·stly

.icalents)lts,ttedthes touralhenlted.adstied1 2

where:

T" = factored tensile load per bolt, kips (kN)

rfi\ = 0.90, strength reduction factor for tension load

P n = nominal tensile capacity of bolt, kips (kN)V no = factored shear force per bolt, kips (kN)

rfi2 = 0.85, strength reduction factor for shear load

Required values of the exponent 'k' differ for various codes. AC1349, AppendixB, states that bolt areas required for tension and for shear shall be additive, implyingk = 1.0. The Uniform Building Code uses k = 5/3. The AISC ASD and AlSC LRFDuse an elliptical interaction curve, which is dependent on the bolt material fordetermining the strength of bolts subject to combined tensions and shear.

A 'k' value of I, in the opinion of this committee, is very conservative. As theinteraction equation is being applied for the steel stresses only, a 'k' value of2 shouldbe used.

(3.4)

where:

F, = the smaller of 1.0 times bolt yield stress or 0.9 times bolt tensile

strengthA, = bolt tensile stress area, in2 (mm2)

(3.5)

3-12

=

f y=

A, =

where:

J1 = friction coefficient from ACI 349, Appendix B= 0.55 ....when the bottom of the base plate is raised above the

concrete surface, as on a grout bed0.70 ....when the bottom of the base plate is on the concrete

surface0.90 ....when the top of the base plate is at or below the concrete

surfaceanchor bolt yield stress, ksi (kPa)

bolt tensile stress area, in2 (mrn2)

b. Allowable stress design

The AISC ASD provides allowable stress design requirements for ASTMA307 (valid for A36), A325, A449. and A490 bolts. The expressions in thespecifications which use stresses based on bolt nominal area, are applicablefor tension alone, shear alone, and combined tension and shear interaction.

For threaded fasteners, per the AISC ASD, the allowable tensile stress is0.33Fu and allowable shear stress is 0.22 Fu (threads excluded from the shearplane) or 0.17 Fu (threads included in shear plane). The AISC ASD does notspecify interaction expressions except for the steels mentioned above. Forother materials a linear interaction expression in the form given below wouldbe conservative:

(3.6)

where:

f, calculated tensile stress, ksi (kPa)

f y = calculated shear stress, ksi (kPa)

F, = allowable tensile stress, ksi (kPa)

F y = allowable shear stress, ksi (kPa)

A 'k' value of I, in the opinion of this committee is conservative and a 'k' value of2 is recommended.

3.6.2 Pullout Failure

A concrete pullout failure occurs when the tensile forces on the anchor boltsproduce principal tensile stresses whIch exceed the capacity of the concrete along a

3-13

i

J

e

e

e

ee

sIr>tIrd

i)

failure surface proj ecting from the bolt head upward at an angle toward the directionof the applied load. This failure surface is what is commonly called the "shear cone"that resembles the model used by ACI 349, Appendix B.

The choice of whether to use the cone model (ACI 349, Appendix B) or thepyramid model (CCD method) is not significant if reinforcement is going to be usedto transfer the design force, as will typically be the case for petrochemical anchoragedesigns. If reinforcement is not required to transfer the design loads or if noreinforcement crosses the failure surface, it is recommended that the engineer use theCCD method as described in the paper by Fuchs, et al. Experimental evidencepresented in this paper indicates that the cone model and equations given by A CI349, Appendix B, may overpredict the capacity of an anchor in unreinforcedconcrete.

Section 3.6 of this document provides recommendations for detailing reinforcingsteel to transfer tensile forces and prevent pullout failure.

3.6.3 Lateral Bursting Failure

Lateral bursting occurs when a deeply embedded anchor is located too close tothe edge of the concrete, resulting in directional differences in restraint stiffnessaround the anchor bolt head and a corresponding lateral strain concentration on theside of the free edge. The result is a cone blowout failure that propagates from thehead of the bolt to the edge of the concrete.

The minimum edge distance required to prevent lateral bursting is discussed inSection 3.7.2.2.

3.6.4 Localized Bearing Failure

3.6.4.1 Background

Traditional design procedures rely upon bond strength to use J-shaped or Lshaped bolts in smaller sizes and use a bolt with a bearing plate in the larger sizes.The plate was sized based on concrete bearing strength. In ACI 349, Appendix B(1980), for instance, bearing strength for small loaded areas is taken as:

[s

a

~fJBn = (2)(0.85)4>(

3-14

(3.7)

where:

¢ = 0.7, strength reduction factorBo = Nominal bearing capacity, ksi (\cPa)

( = 28 day compressive strength, ksi (\cPa)

This calculation gives a fairly large plate size. For example, for a 1-1/2 inch (38mm) bolt, with fy = 36 ksi (250 MPa) and ( = 3 ksi (21 MPa), the required plate

size is 3.82 inches (97 mm) square, normally rounded up to a convenient size.

In ACi 349-82, a drastic revision occurred. The Code said that bearing could beignored, providing that bearing area of the anchor bolt head is at least 1.5 times thetensile stress area. The commentary makes it clear that all normal bolt heads areincluded. The implied bearing strength (ignoring differences in ¢ factors) is 2/3 fy,

which for fy = 36 ksi (250 MPa) and ( = 3 ksi (21 MPa) is 8 (.

ACI 349-90 permits ignoring bearing under ordinary bolt heads of A307, A325,and A490 material. Anchor heads for other materials are also acceptable providedthey have at least the bearing area as above and a thickness equal to 1.0 times thedistance from the edge of the anchor head to the "face of the tensile stresscomponent."

ACI 349 states that if sufficient edge distance is provided to "develop thenecessary confining pressure," crushing of the concrete under the bolt head willnever occur.

3.6.4.2 Recommendations

Based on the latest research. the concrete bearing strength under the bolt head oranchor plate can reach a maximum of

(3.8)

where 0.75 is ¢, the strength reduction factor. Bond strength is assumed tobe zero. Equate the concrete pullout strength with the expression for fastenerstrength:

(3.9)

(This equation is used with factored loads; when nominal loads are used, theallowable bearing can be taken as 4 f~.)

3-15

Then:

(3.10)

18te

Jele

re,

5,~d

Iess

Ie.11

)r

3)

o:r

l)

e

where:

A"",H, = tensile stress area of bolt, in2 (mm2)

Ahead = area of bolt head, in2 (mm2 )

Anomina' = nominal area of bolt, in2 (mm2)

For fy

= 36 ksi (250 MPa) and f; = 3 ksi (21 MPa) the right hand side of the

above equation has a value of 1.3. Since the ratio of head size to bolt size isgreater than this for all available sizes of anchor bolts covered by this report,one can conclude that no special anchor plates are needed when using A36bolts. For higher-strength bolts, Equation 3.10 can be used to determinewhether anchor plates are needed.

3.6.5 Concrete Splitting Failure

Splitting failures are caused by splitting of the structural member before failureof the anchor bolt. Splitting transverse to the tensile force can occur between anchorbolts in multiple bolt anchorages where the spacing between bolts is less than thebolt embedment depth. Also, a splitting failure can occur transverse to the tensionforce if a plane of closely spaced reinforcing steel is located near the embedded endof the anchor bolts.

If the bolts are spaced far enough apart so that (1) either concrete tensile stressarea as recommended by ACI 349 is provided for each bolt or properly developedreinforcing to transfer bolt load to the concrete is provided and (2) if a plane ofclosely spaced reinforcing steel does not exist near the embedded end of the anchorbolts, then a splitting failure should not occur.

3.7 PIER DESIGNIREINFORCING

The anchor bolt/reinforcement system is designed assuming that the anchor bolttension and shear forces are resisted by the pier vertical reinforcement and tiesrespectively. Pier reinforcement is used to resist the anchor bolt tension and shearloads as it is generally not possible to provide the edge distances and bolt spacingsrequired to carry anchorage loads in pier concrete alone.

It is always good detailing practice to include additional reinforcement near thehead of the anchor bolt, particularly when the tensile force on the bolt is high. Ties

3-16

in this area help restrain any unbalanced lateral forces which may result when theconcentrated force at the bolt head is transferred to adjacent reinforcement.

3.7.1 Background

The commentary on Appendix B of ACI 349-90 recommends use of invertedhairpin reinforcement, edge angles attached with reinforcing, and helicalreinforcement to resist tension, shear, and lateral bursting, respectively. Althoughthese provide a valid option from an engineering point of view, their use may causeconstruction difficulties due to congestion of reinforcement.

Therefore, the preferred method for load transfer is as follows:

Tension force transfer tension through vertical pierreinforcement.

Shear force transfer shear through ties in the pier.Lateral bursting force provide minimum edge distance or ties at

bolt head.

3.7.2 Transfer of Tension Force

Tension force in anchor bolts induces tensile stresses in concrete due to directtensile load transfer and lateral bursting forces at the anchor bolt head. Arecommended arrangement of reinforcement for resisting concrete tensile stress inpiers of square, rectangular, and octagonal cross-section is shown in Figures 3.3 and3.4.

3.7.2.1 Tension

Vertical pier reinforcement intercepts potential crack planes adjacent to the bolthead. The reinforcement should be developed on either side of the potential crackplane. Equation 3.11 is used for calculating the area of steel required.

A =~" I/JF y

where:

(3.11 )

tt~

tintiF1<Iitf

A" = the area of vertical pier reinforcement per bolt, in2 (mm2)

T" = factored (ACI 318-89, Chapter 9) tensile load per bolt, kips (kN)F y = minimum specified yield strength of reinforcement steel, ksi (kPa)

I/J= 0.90, strength reduction factor (ACI 318-89. Chapter 9)

3-17

the

rtedicalugh!Use

rectA

Sin

and

Joltack

II)

To be considered effective, the distance of the reinforcement from the anchorbolt head should not exceed the lesser of one-fifth of Ld or 6 inches, where Ld is theembedment length of the anchor bolt. There is no test validation for the one-third Ldspace requirement; however, it has been specified in ACI 349 and has been adoptedin this section as a good practice.

In order to limit the embedment length of a bolt, a larger number of smaller-sizebars is preferred over fewer, larger-size bars. In larger foundations, such as anoctagon, two concentric layers of vertical reinforcement may be provided, as shownin Figure 3.4, if required, to transfer the anchor bolt tensile load.

The arrangement of reinforcement should take into consideration the minimumclearances required for placing and vibrating of concrete, minimum bar spacingrequired by ACI 318, and the need for adequate room below the bolt head or nut toensure there is sufficiently compacted concrete.

The area of vertical pier reinforcement calculated using Equation 3.11 is not tobe considered as additive to the reinforcement required strictly for resisting themoment and tension in sections of the pier. The calculated area of steel required forresisting the external loads applied to the pier should be compared with the area ofsteel required for resisting the tension in the anchor bolts. The area of vertical piersteel provided should equal or exceed the area of steel required for resisting theanchor bolt tension.

3.7.2.2 Lateral Bursting Force

Studies indicate that the minimum edge distance required for preventing lateralbursting of concrete at the bolt head, for ASTM A307 or A36 bolts and high strengthbolts with specified minimum tensile strength equal to or less than 146 ksi (1009MPa), is 4 times bolt diameter and 6 times bolt diameter, respectively. Therefore,the minimum edge distance, based on the bolt material, should be provided for allnew bolt installations. In addition, for high strength bolts two sets of #3 (10 mm)ties at 3 inches (75 mm) spacing should be provided at the bolt head location. SeeFigures 3.3 and 3.4 for arrangement of ties at top and bottom of bolts in piers. Theload transfer method outlined in this section is an extension of the requirementslisted in the ACI 318 and 349 concrete codes and the ACT 355 report. Independenttest to verify the proposed method have not been performed.

3-18

'"u

UICl,f-

Note 5 IIII0:: !

---...... .... i ~ (DIA. OF BOLT)

i~.......

: , ;.,

-, pi• I

l~r::'2 B II ~U'

...,

• " '" ./ I~ ~0

•• ZIII

lLIIII ~ .'" ;-

Ld/3(MAX)......'.

SEE NOTE 1

.......... ANCHOR BOLTS

SEE NOTE 2

SECTIONB

NOTES:I) TO BE CONSIDERED EFFECTIVE FOR RESISTING BOLT TENSION,

THE MAXIMUM DISTANCE FROM ANCHOR HEAD TO THEREINFORCEMENT SHALL BE Ld/3.

2) INTERIOR TIES TO BE PROVIDED IF REQUIRED PER ACl318.

3) A MINIMUM OF 2 SETS OF TIES AT 3 INCH SPACING, CENTERED ATBOLT HEAD LOCATION, FOR HIGH-STRENGTH BOLTS ONLY. (SEESECTION 3.7.2.2)

4) Id ~ DEVELOPMENT LENGTH OF PIER REINFORCMENT.Ld ~ EMBEDMENT LENGTH OF ANCHOR BOLT

5) 4d OR 4-1/2" MIN FOR ASTM A307/A36 BOLTS. 6 d OR 4-1/2" MINFOR HIGH STRENGTH BOLTS (SEE SECTION 3.7.2.2)

Figure 3.3: Reinforcement for Resisting Bolt Tension in Square andRectangular Pedestals

3-19

~

~

t~NOTE5 I in; d(DIA.OFBOLT)

....------i---....j

REINFORCEMENT

C

NOTES,

1) TO BE CONSIDERED EFFECTIVEFOR RESISTING BOLT TENSION,THE MAXIMUM DISTANCEFROM ANCHOR HEAD TO THEREINFORCEMENT SHALL BE Ld/3.

2) A MINIMUM OF 2 SETS OF TIESAT 3 INCH SPACING, CENTEREDAT BOLT HEAD LOCATION, FORHIGH STRENGTH BOLTS ONLY.(SEE SECTION 3.7.2.2)

3) Id = DEVELOPMENT LENGTH OFPIER REINFORCMENT.

4) Ld=EMBEDMENT LENGTH OFANCHOR BOLT

5) 4d OR 4-1/2" MIN FOR ASTMA307/A36 BOLTS.6d OR 4-1/2" MIN FORHIGH-STRENGTH BOLTS. (SEESECTION 3.7.2.2)

SEE NOTE 2

PROVIDE 2 LAYERS OF VERTICAL BARS IFREQUIRED BY DESIGN FOR TRANSFER OFANCHOR BOLT TENSION

Ld/3 MAX.)SEE NOTE 1

'":s z

"-en~

en Cl-< P::

" ~

Z -- ""U >--< ~

"" cien~ 0'E=: gj

SECTIONC

Figure 3.4: Reinforcement for Resisting Bolt Tension in Octagons

3-20

3.7.3 Transfer of Shear Force

Failure due to inadequate edge distance consists of breakout of a half prism orcone of concrete from centerline of bolt to face of pier in the direction of the shearforce. If multiple bolts exist, then the failure prism/cones overlap. To reinforce theconcrete in the failure plane, 2 sets of ties are provided at the top of piers. The firstset is located at a maximum distance of 2 inches (50 mm) from top of concrete. Thespacing between the two sets of ties should be 3 inches (75 mm).

Arrangement of ties to resist shear force in square and rectangular piers is shownin Figure 3.5. Transfer of shear force in octagons is generally not a problem andhence a detail has not been developed. Equation 3.12 is used to calculate the area ofsteel required to resist the shear force (factored load).

VA =__u_

" ¢Fyn

where:

(3.12)

A"V, =

Fy=

area of reinforcement required. Area of one leg of tie, in2 (mm2).

factored shear force resisted by anchor bolt(s), kips (kN)minimum specified yield strength of reinforcement steel, ksi

(kPa)n = number of legs in the top 2 sets of ties resisting the shear force

In Figure 3.5 the failure plane only intersects the top tie, thereforein this situation for Section A n = I, for Section B n = 2.

¢ 0.85, strength reduction factor

The arrangement of reinforcement should consider the minimum clearancesrequired for placing and vibrating of concrete and minimum bar spacing required byACI318. For large shear forces, shear lugs should be provided for transfer ofloads.Also, in low seismic zones, shear may be transferred by friction between the baseplate and top of pier, and anchor bolts may be used for transfer of tension only. Theload transfer method outlined in this section is an extension of the requirementslisted in ACI 318, 349, and 355./. Independent test to verify the proposed methodhave not been performed.

3-21

j

-l'!QIf~- d (OIA. OF BOLT)~ -"------

• SHEAR FORCE

- STDHOOK

,

I, ,"

CLOSED TIES, "U" BARS OR "J" BAR~

\

CAN BE USED, DEPENDING UPON TIFAILURE t ~ AVAILABLE EMBEDMENT SPACEPLANE; ~

j1i?;;:;:::;:=:::;'1~\

STDHOOK

,own

and~a of

1.12)

mar:heare thefirstThe

fore SECTION A SECTIONB

lees:iby'ads.JaseTheentshod

SHEAR CAPACITY OF TIES IS BASED ON NUMBER OF LEGS THATINTERCEPT FAILURE PLANE IN PLAN AND ELEVATION. DEVELOPMENTLENGTH FOR TIE LEG MUST BE PROVIDED IN ORDER FOR TIE TO BEFULLY EFFECTIVE.

NOTES:

1) 4d OR 4 112" MIN FOR ASTM A307/A36 BOLTS. 6d OR 4 1/2" MIN FORHIGH-STRENGTH BOLTS. (SEE SECTION 3.7.3.2).

Figure 3.5: Reinforcement for Resisting Bolt Shear in Square and RectangularPedestals

3-22

CHAPTER 4INSTALLATION

4.1 INTRODUCTION

This chapter provides basic information regarding installation of anchor boltswith regard to sleeves, pretensioning, and considerations of vibratory or seismicloads.

4.2 SLEEVES

Sleeves are used with anchor bolts when a small movement of the bolt is desiredafter the bolt is set in concrete. This is generally required for one of the followingtwo conditions:

a. When precise alignment of anchor bolts is required during installation ofstructural columns and/or equipment.

b. When anchor bolts are to be pretensioned in order to maintain the bolt undercontinuous tensile stresses during load reversal generated by high-pressurepiping anchors, vibrating equipment, and/or wind on tall structures andprocess vessels.

For condition a., sleeves should be filled with grout after installation. However,for condition b., sleeves should be sealed on top or filled with an approvedelastomeric material to prevent grout or water from filling the sleeve.

4.2.1 Types of Sleeves

Two types of sleeves are commonly used with anchor bolts. The first type is apartial sleeve as shown in Figure 4.1, which is typically used for alignment purposesonly. The second type is a full sleeve as shown in Figure 4.2, which is used foralignment purposes as well as for pretensioning the bolt.

4-1

CONCRETE--. r-- GROUT,

. -.' .

I,

Figure 4.1: Sleeve Used for Alignment Purposes

WRAP #10 fELT AROUNDr A.B. ABOVE SLEEVE TO/ BREAK BOND

STDPIPESLEEVE

ANCHOR BOLT

F- ANCHOR PLATE

'.', "

/

BAC~ROD

/TACK '" /WELD /'-----~7---+-0

Figure 4.2: Sleeve Used for Alignment Purposes and Pre-Tensioning

4-2

4.2.2 Design Considerations

Sleeves will not affect the design of headed anchor bolts subjected to tensileloads, because the tension in the bolt is transferred to the concrete via the anchor bolthead and not by the bond between the bolt and the concrete.

In the design of an anchor bolt with a partial sleeve, the embedment depth of thebolt should be determined as recommended in Chapter 3. However, the distancebetween the bottom of the sleeve and the anchor-bearing surface should be sufficientto ensure that the concrete below the sleeve will not fail in shear from tensile loadscausing the bolt head to snap through the sleeve. The' minimum distance betweenthe bottom of the sleeve and the anchor bearing surface should not be less than 6bolt diameters or 6 inches (150 mm), whichever is greater.

The applied shear force may be resisted by anchor bolts only if the sleeves arefilled with grout. If the sleeves are not filled with grout, the anchor bolts will not beeffective in resisting the applied shear force. The sleeve, combined with isolation ofthe bolt from the grout, is desirable to prevent short radius flexing of the anchor boltdue to a horizontal component of the vibration or as a result of thermal growth of theequipment and is an effective way to avoid the most common failure mode ofcompressor anchor bolts.

4.3 PRETENSIONING

Certain conditions make it desirable to pretension anchor bolts to enhance theperformance of the bolt or the performance of the system.

The recommended pretension load is one-third the tensile strength of the boltunless otherwise required.

Anchor bolts may need to be retightened one week after initial pretensioning tocompensate for pre-load losses from strain relaxation within the system.

4.3.1 Pretension Applications

Pretensioning of anchor bolts should be used for the following situations:

a. Tall process towers sensitive to wind (as a rule of thumb these are towersover 100 feet (30 meters) tall or with a hcight-to-diameter ratio of 15 ormore).

b. Reciprocating compressors or other pulsating or vibrating equipment.

c. High-strength anchor bolts (to prevent load reversals on bolts susceptible tofatigue weakening).

4-3

t

1

ft

f

4.3.2 Development

Pretensioned anchor bolts should be designed for an embedment development ofat least 80% of their ultimate capacity (0.8 fud.

4.3.3 Methods

Methods that may be utilized to apply the required pre-load are as follows:

a. Hydraulic jacking

Hydraulic jacking is the most accurate method and is recommended if thehydraulic equipment is available and if the physical clearances that exist aroundeach bolt permit its use.

b. Turn-of-nut

Turn-of-nut is the easiest to perform by a construction crew and gIves areasonably accurate result provided that:

*

*

Conditions of grout and base plate can give a consistent "snug-tight" result

Stretching (spring) length of bolt can be accurately determined.

t

. 360 I AfTNut RotatIOn = t t k

EAd

where:

(4.1)

)= bolt stretch length, in (mm)= tensile stress area of bolt, in2 (mm2)

= desired tensile stress, ksi (kPa)= bolt threads per unit length, thds/in (thds/mm)

elastic modulus of bolt, ksi (kPa)= nominal bolt area, in2 (mm2)

o

If the bolt is to be retightened to compensate for any loss of pre-load, thismethod requires that nuts be loosened, brought to a "snug tight" condition, and thenturned the number of degrees originally specified.

c. Torque wrench

Torque wrench pretensioning provides only a rough measure of actual pretensionload but can be the method of choice if equipment for item a. is not available and

4-4

stretch length of anchor cannot be fixed as required by the "tum of nut" method.The Industrial Fastener Institute recommends the following fonnula for detenniningthe proper tightening torque.

T=KDP

where:

T = tightening torque, kip-in (kN-mm)K = torque coefficient, dimensionlessD = fastener diameter, nominal, in (mm)P = bolt tensile load, kips (kN)

"K" varies from 0.06 to 0.35 (use 0.20 for typical anchor bolt)

4.3.4 Stretching Lengths

(4.2)

Pretensioning should only be implemented when the stretching (spring) length ofthe anchor bolt extends down to near the anchor head of the bolt. On a typicalanchor bolt embedment, as a pre-load is placed upon the bolt, the bolt starts to shedits load to the concrete through its grip (bond) on the bolt. At that time, there existsa high bond stress at the first few inches of embedment. This bond will relieve itselfover time and thereby reduce the pre-load on the bolt. Therefore, it is important thatthe bond be prevented on anchor bolts to be pretensioned. Bond on the bolt shaftcan be prevented by wrapping the shaft with plastic tape or by heavily coating thebolt with grease immediately before placing concrete. Grout must not be allowed tobond to the anchor bolt. Tape the portion of the anchor bolt through the grout zoneand to within one inch (25 mm) of the bolt head, below the sleeve. (See Figure 4.3)

Tape or grease should not be applied closer than one inch (25 mm) to the anchorbolt head or anchor plate. Anchor bolt sleeves should not be positioned closer than6D to the bolt head to preclude failure by the head of the bolt pulling through thesleeve.

Sleeved anchor bolts to be pretensioned should have that portion of the boltbeneath the sleeve taped or greased.

The stretching length of the bolt which is pre-loaded within the elastic range actsas a spring in clamping the base plate down against the foundation.

4-5

TAPE

--- BASE PL

-E:ti~~V GROUTI- ·~FDN., A. BOLT

=>.~-

l$l\....---+-- A.BOLT SLEEVE. --/-------r '":'

:/2' J~t~~

--T.O. ROUGHCONCRETE

TAPE_

A. BOLTC-.-----'.--\--~i.I.1FDN. 8

BASEPL -

GROUT

NOTE: STRETCHING LENGTH ~ THAT PORTION OF ANCHOR BOLTALLOWED TO FREELY STRETCH.

Figure 4.3: Anchor Bolt Stretch Length

4.3.5 Tightening Sequence

Anchor bolts should be tightened in two stages:

a. First stage should apply 50% of full pre-tension load to all bolts.

b. Second stage should apply full pre-tension load to all bolts.

Bolts should be tightened in a criss-cross pattern. (See Figure 4.4 for circularbolt pattern sequence.)

;112 ...___- ~__ . 5

8

f/" . .,:

4L \ c EQUIPMENT

\ ~10\ /~

\~T/'11

TIGHTENING SEQUENCE

Figure 4.4: Anchor Bolt Tightening Sequence

4-6

4.4 CONSIDERATIONS FOR VIBRATORY LOADS

4.4.1 Sleeves

Provide sleeves on all anchor bolts installed on vibratory equipment and isolatebolt from any grout (see Figure 4.5).

4.4.2 Pretensioning

Pretension all anchor bolts installed on vibratory equipment, unless specificallyprohibited by the manufacturer.

This pretensioning (stretching) of the anchor bolts creates a spring effect thatwill absorb the vertical amplitude of the vibration without fatiguing. This springeffect also serves well in clamping the equipment base against the grout without thenut loosening if the amount of anchor bolt stretch exceeds the vertical amplitude ofthe vibration.

4.5 CONSIDERATIONS FOR SEISMIC LOADS (ZONES 3 AND 4)

Anchorage capacity, including capacity of reinforcement, must exceed minimumspecified tensile strength (based on fut) of the bolt to ensure that any reserve capacityof the bolt can be utilized and that the failure mode will be ductile and in the bolts.

Friction capacity from gravity loads shall not be considered effective in carryingany seismic lateral loads.

Friction capacity may be considered if anchor bolts are pretensioned to twice thecalculated seismic uplift force. Friction may then be considered, except frictionshall not exceed 50% of that provided by pretension loads.

4-7

FILL ANCHOR BOLTSLEEVE WITHELASTOMERICMATERIAL.

FOAM INSULATION

PRE-TE"SIONED ANCHOR BOLTSIN ACCORDANCE ''nTH VENDOR'SINSTRUCTIONS OR DESIGN DWG.

ASE PLATE

___GROUT

•. o.

ANCHOR BOLTSLEEVE

'. . .. .. - ... ."., •. ~ L.._....__----....,:". 1-.·. ~ ;-. . '.' '.C. I.-.0: •.•... "0 -0-:•.A.. ~ ...'.Ie

••,' :,.:'~'':;'';";':.:;,'',;;:.,.'l.,J A •• • ••••• ~

"'lI • • •• •

•• :3 •• ~-_.I. ;:l.• •• jj

C···· d .-4°'.~

'0 d' ~.• •••

co

a .4 •

o

CONCRETEPEDESTAL

Figure 4.5: Detail for Anchor Bolt for Vibrating Equipment

4-8

Ad =

A,f[ =

A"A" =

A, =

NOMENCLATURE

nominal boIt areaeffective anchor bolt area for resisting tension

the area of vertical pier reinforcement per bolt

area of cross-section of one leg of tieanchor bolt tensile stress area

BC = bolt circle diameterB, = nominal bearing capacity

D = fastener diameter

E = elastic modulus of bolt

f, actual tensile stressF, = allowable tensile stress

f, = actual shear stress

F, = allowable shear stress

f y = anchor bolt yield stress

Fy = minimum specified yield strength of reinforcement steel

K torque coefficient

= bolt stretch length

M = maximum moment on vessel

n = number oflegs in the top 2 sets of ties resisting the shear force (Vu)N number of anchor bolts

P bolt tensile loadP, = nominal tensile capacity of bolt

T tightening torqueT k bolt threads per unit length

T" = factored tensile load per bolt

V" factored shear force resisted by anchor bolt(s) located in the pier

V"" = factored shear force per bolt

W = mmimum weight of vessel

A-I

Jl friction coefficient

I/> = strength reduction factor1/>1 = strength reduction factor for tension load1/>2 = strength reduction factor for shear load

A-2

REFERENCES

ACI AB-81, American Concrete Institute, Guide 10 the Design ofAnchor Bolts andother Steel Embedments.

ACI 222, American Concrete Institute, Corrosion ofMetal in Concrete.

ACI 318-89, American Concrete Institute, Building Code Requirements forReinforced Concrete.

ACI 349-82, American Concrete Institute, Code Requirements for Nuclear SafetyRelated Concrete Structures.

ACI 349-90, American Concrete Institute, Code Requirements for Nuclear SafetyRelated Concrete Structures.

ACI 355.1-R91, American Concrete Institute, State of the Art Report on Anchorageto Concrete.

AISC ASD, American Institute of Steel Construction, Specification for StructuralSteel Buildings, Allowable Stress Design and Plastic Design, June I, 1989.

AISC ASD Manual, American Institute of Steel Construction, Manual of SteelConstruction: Allowable Stress Design, Ninth Edition, 1989.

AISC LRFD, American Institute of Steel Construction, Manual of SteelConstruction: Load and Resistance Factor Design, First Edition, 1986.

AISC LRFD Manual, American Institute of Steel Construction, Load andResistance Factor Design Specification for Structural Steel Buildings, September I,1986.

API 620, American Petroleum Institute, Recommended Rules for Design andConstruction of Large, Welded, Low-Pressure Storage Tanks, Seventh Edition,September 1982 (Revision I-April 1985).

API 650, American Petroleum Institute, Welded Steel Tanks for Oil Storage, NinthEdition, July 1993.

ASTM A36, American Society for Testing and Materials, Specification forStructural Steel, 199 I.

ASTM A143, American Society for Testing and Materials, Practice forSafeguarding Against Embrittlement of Hot-Dip Galvanized Structural SteelProducts and Procedure for Detecting Embrittlement, 1974 (Revised 1989).

B-1

ASTM A153, American Society for Testing and Materials, Specification forZincCoating (Hot-Dip) on Iron and Steel Hardware, 1987.

ASTM A193, American Society for Testing and Materials, Specification for AlloySteel and Stainless Steel Bolting Materialsfor High-Temperature Service, 1992.

ASTM A307, American Society for Testing and Materials, Specification for CarbonSteel Bolts and Studs, 60,000 psi Tensile, 1992.

ASTM A325, American Society for Testing and Materials, Specification forStructural Bolts, Steel, Heat-Treated, 1201105 ksi Minimum Tensile Strength, 1992.

ASTM A449, American Society for Testing and Materials, Specification forQuenched and Tempered Steel Bolts and Studs, 1992.

ASTM A490, American Society for Testing and Materials, Specification for HeatTreated, Steel Structural Bolts, 150 ksi (1035 MPa) Tensile Strength, 1992.

ASTM A588, American Society for Testing and Materials, Specification for HighStrength, Low-Alloy Structural Steel with 50 ksi (345 MPa) Minimum Yield Point to4 in. (l00 mm)Thick, 1991.

ASTM A767, American Society for Testing and Materials, Specification for ZincCoated (Galvanized) Bars for Concrete Reinforcement, 1990.

ASTM A775, American Society for Testing and Materials, Specification for EpoxyCoated Reinforcing Steel Bars, 1992.

ASTM A780, American Society for Testing and Materials, Practice for Repair ofDamaged and Uncoated Areas ofHot-dip Galvanized Coatings, 1992.

Bailey and Burdette, John W. Bailey and Edwin G. Burdette, Edge Effects onAnchorage to Concrete, Civil Engineering Research Series No. 31, The Universityof Tennessee at Knoxville, 1977.

Blodgett, Orner Blodgett, Design of Welded Structures, The James F. Lincoln ArcWelding Foundation, Cleveland, Ohio, 1966.

Cook and KIingner, Ronald A. Cook and Richard E. Klingner, "Behavior ofDuctile Multiple Anchor Steel to Concrete Connections with Surface MountedBaseplates", ACI SP 130, Anchors in Concrete Design and Behavior, 1991.

B-2

Fuchs et ai, Werner Fuchs, Rolf Eligehausen, John Breen, Concrete CapacityDesign (CCD) Approach for Fastening to Concrete, ACI Structural Journal, Vol. 92,No. I, January/February, 1995.

Furche et ai, Johannes Furche, and Rolf Eligehausen, "Lateral Blowout Failure ofHeaded Studs near a Free Edge", ACI SPI30 Anchors in Concrete -- Design andBehavior", American Concrete Institute, Detroit, 1991.

Hasselwander, Jirsa, Breen and Lo, G.B. Hasselwander, J.O. Jirsa, J.E. Breen, andK. Lo, Strength and Behavior ofAnchor Bolts Embedded Near Edges of ConcretePiers, Research Report 29-2F, Center for Highway Research, The University ofTexas at Austin, 1977.

Industrial Fasteners Institute, Fastener Standards, Sixth Edition, p. M-64.

Lee and Breen, D.W. Lee and J.E. Breen, Factors Affecting Anchor BoltDevelopment, Research Report 88-IF, Center for Highway Research, The Universityof Texas at Austin, 1966.

Steel Design Guide Series, Volume 1, John T. Dewolf, Steel Design Guide Series,Design ofColumn Base Plates, American Institute of Steel Construction, 1990.

Steel Design Guide Series,Volume 7, James M. Fisher, Steel Design Guide Series,Industrial Buildings, Roofs to Column Anchorage, American Institute of SteelConstruction, 1993.

Uniform Building Code, International Conference of Building Officials, Whittier,California, 1991.

B-3

J!

INDEX

AAllowable stress design 3-13American Concrete Institute (ACI) 3-1,

3-5,3-15,3-18,3-21; ACl349,Appendix B 1-1, 1-2, 3-1-3-3, 314; ACI Publication AB-81 1-1 ;and CCD 3-1; committees 1-2;corrosion codes and specifications2-3-2-4

American Institute of Steel Construction(AISC) 2-4, 3-13

American Petroleum Institute (API) 2-4American Society for Testing Materials

(ASTM) 2-5, 2-6, 3-3, 3-18; andbolt materials 2-2

Anchorage capacity 3-1-3-3Anchorage failure 3-6, 3-10-3-16Anchor bolts (cast-in-place, headed

bolts): coatings and corrosion prcrtections 2-1-2-7; codes andspecifications 1-1-1-2 2-3-2-4', ,common materials 2-2; configuration 3-4; design considerations 33-3-7; design methods 3-1-3-3;failure modes 3-10-3-16; forcedistribution 3-7-3-10; pretensionapplications 4-3-4-6; reinforcement systems 3-16-3-22; sleeves4-1-4-3; tightening sequence 46; vibratory and seismic loads 47-4-8

BBearing failure, localized 3-14-3-16Biaxial loads, design method changes

3-2Bolt configuration 3-3-3-4Bolt loads 3-1 1Bolt shear 3-21-3-22

I-I

Bolt tension 3-1 7-3-1 9

CCoatings, corrosion prevention 2-4-

2-7Codes 1-2, 2-3-2-6Cold-applied zinc 2-6Concrete bearing strength 3-15-3

16Concrete Capacity Design (CCD)

method 1-2, 3-1-3-3Concrete splitting failure 3-16Cone model 3-1-3-2, 3-14Configurations: anchor bolts lcast-in-

place, headed bolt) 3-4; designflowchart 3-6; octagonal pedestalreinforcement 3-20; square andrectangular pedestals reinforcement 3-19; stretch length 4-6;tightening sequence 4-6

Corrosion 2-1, 2-3-2-7Corrosion allowance 2-5Corrosion rates 2-4

oDesign basis 3-4-3-7Design load, considerations 3-5Design methods 1-2, 3-1-3-3Ductile connections: defined 3-5, 3-7;

and shear 3-10

EElectrcrdeposited zinc coating 2-6Environmental conditions, corrosion 2-

3Equotions: allowable stress design

expression (3.6) 3-13; bearingstrength, Bn (3.7) 3-14-3-16; con·crete pullout and fastener strengths

(3.8-3.10) 3-15-3-16; maximumtension (3.1) 3-8; nut rotation (4.1)4-4; reduced anchor bolt area, Aeff(3.2) 3-9; shear, reinforcementarea, Asv (3.12) 3-21; torque formula, T (4.2) 4-5; ultimate strengthdesign, Pn (3.3-3.5) 3-12-3-13;vertical pier reinforcement area, Ast(3. 11) 3- 17-3-18

FFactored service loads 3-5Failure modes 3-10-3-16Fastener strength 3-1 5-3-1 6Fireproofing 2-6Force distribution 3-7-3-10Foundation designs 3-3Full sleeve 4-1, 4-2

GGalvanized bolts 2-1, 2-5-2-6Grades, anchor bolt materials 2-1, 2-

2

HHot dip zinc 2-5-2-6Hydraulic jacking method 4-4

IIndustrial Fastener Institute 4-5Insulation 2-6

LLateral bursting failure 3-14Loads, bolt 3-1 1

MMoment of inertia 3-8

NNonductile connections: defined 3-7·,

1-2

and shear 3-10

oOne-third Ld space requirement 3-18

p

Partial sleeve 4-1, 4-2, 4-3Pickling process 2-1Pier design 3-16-3-17Pier reinforcement 3-17-3-22Plates, bearing 3-14-3-16Pretension applications 4-3-4-7Pullout failure 3-13-3-14Pyramid model 3-1-3-2, 3-14

5Seismic loads 4-7Shear: design method changes 3-2;

distribution of 3-10; forces 321-3-22; shear cone 3-1 3-314; and tension 3-12-3-13

Sleeves 4-1-4-3Specifications, and codes 2-3-2-6Splitting failure, concrete 3-16Strength design 3-12-3-13Stress design, bolt failure 3-13Stretching (spring) lengths 4-5-4-6Structural column anchorage 3-8-3-

10

TTensile stress: bolt failure 3-11-3-14;

lateral bursting (blowout) failure 3

18Tension: design method changes 3-2;

equation 3-8; lateral burstingforce 3-1 8; and shear 3-1 2-313; vertical pier reinforcement 317-3-18

Torque wrench method 4-4-4-5Turn-of-nut method 4-4

UUltimate strength design 3-12-3-13Ultimate tensile capacity 3-5Uniform Building Code IUBC) 3-12

VVertical pier reinforcement area 3

17-3-18Vertical vessel anchorage 3-8Vibratory loads 4-7

WWeathering steels 2-6-2-7

1-3

;

"::.:....·0··

,;::'.'0:":(~:1~~:ii·.

r:f :

rf

These committee reports provide state-of-the-practice guidelines forthe determtpationofWind indul:;ed forces and the design of headed,

, el(ample~" dreseatch',ana?jjre~~Jre;;~s'sefrTh~, " " .",'che,tnical industrY anchoiJ>o ,,' d~si91) methoas~ r(jpo~1idChangesand, new releases of design codes, and provides recomr:li~ndations

that supplement current codes for design ofhel;:ided, Pdst-in-placeaiu;J'!pr 'b9Its:. Subject ar~as illcludethe current :~til!eof research,gfQi;!E!s, fabi-i~ationand weldilJg, corrosion; ,bolt 'cohfiguration anddimensions, distribution ,of 'an,chor bolt f()rces,.cllecking criticalmodes offailure, pier desigrl/reinforcing, pretensionlng;and consid-erl:lfions for vibratory and seismic loads. '" '

II

9 780784 402627

ISBN 0-7844-0262-0 ItI

Wind Loads _ Anchor Bolt Design for Petrochemical Facilities

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